diff --git a/render/container.go b/render/container.go
index 5a20984ea..ada6f03ba 100644
--- a/render/container.go
+++ b/render/container.go
@@ -103,13 +103,7 @@ func FilterEmpty(topology string, r Renderer) Renderer {
 // topology.
 func HasChildren(topology string) FilterFunc {
 	return func(n report.Node) bool {
-		count := 0
-		n.Children.ForEach(func(child report.Node) {
-			if child.Topology == topology {
-				count++
-			}
-		})
-		return count > 0
+		return len(n.ChildIDs) > 0
 	}
 }
 
diff --git a/render/detailed/connections.go b/render/detailed/connections.go
index dbf35b607..3159fc79a 100644
--- a/render/detailed/connections.go
+++ b/render/detailed/connections.go
@@ -167,7 +167,7 @@ func (c *connectionCounters) rows(r report.Report, ns report.Nodes, includeLocal
 }
 
 func incomingConnectionsSummary(topologyID string, r report.Report, n report.Node, ns report.Nodes) ConnectionsSummary {
-	localEndpointIDs, localEndpointIDCopies := endpointChildIDsAndCopyMapOf(n)
+	localEndpointIDs, localEndpointIDCopies := endpointChildIDsAndCopyMapOf(r, n)
 	counts := newConnectionCounters()
 
 	// For each node which has an edge TO me
@@ -175,7 +175,7 @@ func incomingConnectionsSummary(topologyID string, r report.Report, n report.Nod
 		if !node.Adjacency.Contains(n.ID) {
 			continue
 		}
-		for _, remoteEndpoint := range endpointChildrenOf(node) {
+		for _, remoteEndpoint := range endpointChildrenOf(r, node) {
 			for _, localEndpointID := range remoteEndpoint.Adjacency.Intersection(localEndpointIDs) {
 				localEndpointID = canonicalEndpointID(localEndpointIDCopies, localEndpointID)
 				counts.add(r.DNS, false, n, node, r.Endpoint.Nodes[localEndpointID], remoteEndpoint)
@@ -197,7 +197,7 @@ func incomingConnectionsSummary(topologyID string, r report.Report, n report.Nod
 }
 
 func outgoingConnectionsSummary(topologyID string, r report.Report, n report.Node, ns report.Nodes) ConnectionsSummary {
-	localEndpoints := endpointChildrenOf(n)
+	localEndpoints := endpointChildrenOf(r, n)
 	counts := newConnectionCounters()
 
 	// For each node which has an edge FROM me
@@ -206,7 +206,7 @@ func outgoingConnectionsSummary(topologyID string, r report.Report, n report.Nod
 		if !ok {
 			continue
 		}
-		remoteEndpointIDs, remoteEndpointIDCopies := endpointChildIDsAndCopyMapOf(node)
+		remoteEndpointIDs, remoteEndpointIDCopies := endpointChildIDsAndCopyMapOf(r, node)
 		for _, localEndpoint := range localEndpoints {
 			for _, remoteEndpointID := range localEndpoint.Adjacency.Intersection(remoteEndpointIDs) {
 				remoteEndpointID = canonicalEndpointID(remoteEndpointIDCopies, remoteEndpointID)
@@ -228,27 +228,31 @@ func outgoingConnectionsSummary(topologyID string, r report.Report, n report.Nod
 	}
 }
 
-func endpointChildrenOf(n report.Node) []report.Node {
+func endpointChildrenOf(r report.Report, n report.Node) []report.Node {
 	result := []report.Node{}
-	n.Children.ForEach(func(child report.Node) {
-		if child.Topology == report.Endpoint {
-			result = append(result, child)
+	for _, childID := range n.ChildIDs {
+		if ty, ok := report.NodeIDType(childID); ok && ty == report.Endpoint {
+			if child, found := r.Endpoint.Nodes[childID]; found {
+				result = append(result, child)
+			}
 		}
-	})
+	}
 	return result
 }
 
-func endpointChildIDsAndCopyMapOf(n report.Node) (report.IDList, map[string]string) {
+func endpointChildIDsAndCopyMapOf(r report.Report, n report.Node) (report.IDList, map[string]string) {
 	ids := report.MakeIDList()
 	copies := map[string]string{}
-	n.Children.ForEach(func(child report.Node) {
-		if child.Topology == report.Endpoint {
-			ids = ids.Add(child.ID)
-			if copyID, _, ok := child.Latest.LookupEntry(endpoint.CopyOf); ok {
-				copies[child.ID] = copyID
+	for _, childID := range n.ChildIDs {
+		if ty, ok := report.NodeIDType(childID); ok && ty == report.Endpoint {
+			ids = ids.Add(childID)
+			if child, found := r.Endpoint.Nodes[childID]; found {
+				if copyID, _, ok := child.Latest.LookupEntry(endpoint.CopyOf); ok {
+					copies[child.ID] = copyID
+				}
 			}
 		}
-	})
+	}
 	return ids, copies
 }
 
diff --git a/render/detailed/node.go b/render/detailed/node.go
index d96a739ed..2dc246e47 100644
--- a/render/detailed/node.go
+++ b/render/detailed/node.go
@@ -223,16 +223,20 @@ var nodeSummaryGroupSpecs = []struct {
 
 func children(rc RenderContext, n report.Node) []NodeSummaryGroup {
 	summaries := map[string][]NodeSummary{}
-	n.Children.ForEach(func(child report.Node) {
-		if child.ID == n.ID {
-			return
+	for _, childID := range n.ChildIDs {
+		if childID == n.ID {
+			continue
 		}
-		summary, ok := MakeNodeSummary(rc, child)
-		if !ok {
-			return
+		if ty, ok := report.NodeIDType(childID); ok {
+			if topology, ok := rc.Report.Topology(ty); ok {
+				if child, ok := topology.Nodes[childID]; ok {
+					if summary, ok := MakeNodeSummary(rc, child); ok {
+						summaries[ty] = append(summaries[ty], summary.SummarizeMetrics())
+					}
+				}
+			}
 		}
-		summaries[child.Topology] = append(summaries[child.Topology], summary.SummarizeMetrics())
-	})
+	}
 
 	nodeSummaryGroups := []NodeSummaryGroup{}
 	// Apply specific group specs in the order they're listed
diff --git a/render/expected/expected.go b/render/expected/expected.go
index 7ce945e74..efa9038f8 100644
--- a/render/expected/expected.go
+++ b/render/expected/expected.go
@@ -51,28 +51,26 @@ var (
 
 	unknownPseudoNode1 = func(adjacent ...string) report.Node {
 		return pseudo(UnknownPseudoNode1ID, adjacent...).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.UnknownClient1NodeID],
-				RenderedEndpoints[fixture.UnknownClient2NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.UnknownClient1NodeID,
+				fixture.UnknownClient2NodeID,
 			))
 	}
 	unknownPseudoNode2 = func(adjacent ...string) report.Node {
 		return pseudo(UnknownPseudoNode2ID, adjacent...).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.UnknownClient3NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.UnknownClient3NodeID,
 			))
 	}
 
 	theIncomingInternetNode = func(adjacent ...string) report.Node {
 		return pseudo(render.IncomingInternetID, adjacent...).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.RandomClientNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.RandomClientNodeID,
 			))
 	}
 
-	theOutgoingInternetNode = pseudo(render.OutgoingInternetID).WithChildren(report.MakeNodeSet(
-		RenderedEndpoints[fixture.GoogleEndpointNodeID],
-	))
+	theOutgoingInternetNode = pseudo(render.OutgoingInternetID).WithChildID(fixture.GoogleEndpointNodeID)
 
 	RenderedEndpoints = report.Nodes{
 		fixture.Client54001NodeID:    endpoint(fixture.Client54001NodeID, fixture.Server80NodeID),
@@ -93,24 +91,16 @@ var (
 				process.PID:       fixture.Client1PID,
 				process.Name:      fixture.Client1Name,
 			}).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-			)),
+			WithChildID(fixture.Client54001NodeID),
 
 		fixture.ClientProcess2NodeID: processNode(fixture.ClientProcess2NodeID, fixture.ServerProcessNodeID).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54002NodeID],
-			)),
+			WithChildID(fixture.Client54002NodeID),
 
 		fixture.ServerProcessNodeID: processNode(fixture.ServerProcessNodeID).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-			)),
+			WithChildID(fixture.Server80NodeID),
 
 		fixture.NonContainerProcessNodeID: processNode(fixture.NonContainerProcessNodeID, render.OutgoingInternetID).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.NonContainerNodeID],
-			)),
+			WithChildID(fixture.NonContainerNodeID),
 
 		// due to https://github.com/weaveworks/scope/issues/1323 we are dropping
 		// all non-internet pseudo nodes for now.
@@ -124,26 +114,26 @@ var (
 		fixture.Client1Name: processNameNode(fixture.Client1Name, fixture.ServerName).
 			WithLatests(map[string]string{process.Name: fixture.Client1Name}).
 			AddCounter(report.Process, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
 			)),
 
 		fixture.ServerName: processNameNode(fixture.ServerName).
 			WithLatests(map[string]string{process.Name: fixture.ServerName}).
 			AddCounter(report.Process, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.ServerProcessNodeID,
 			)),
 
 		fixture.NonContainerName: processNameNode(fixture.NonContainerName, render.OutgoingInternetID).
 			AddCounter(report.Process, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.NonContainerNodeID],
-				RenderedProcesses[fixture.NonContainerProcessNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.NonContainerNodeID,
+				fixture.NonContainerProcessNodeID,
 			)),
 
 		// due to https://github.com/weaveworks/scope/issues/1323 we are dropping
@@ -155,9 +145,9 @@ var (
 	}
 
 	uncontainedServerID   = render.MakePseudoNodeID(render.UncontainedID, fixture.ServerHostID)
-	uncontainedServerNode = pseudo(uncontainedServerID, render.OutgoingInternetID).WithChildren(report.MakeNodeSet(
-		RenderedEndpoints[fixture.NonContainerNodeID],
-		RenderedProcesses[fixture.NonContainerProcessNodeID],
+	uncontainedServerNode = pseudo(uncontainedServerID, render.OutgoingInternetID).WithChildren(report.MakeIDList(
+		fixture.NonContainerNodeID,
+		fixture.NonContainerProcessNodeID,
 	))
 
 	RenderedContainers = report.Nodes{
@@ -168,17 +158,17 @@ var (
 				docker.ContainerName: fixture.ClientContainerName,
 				docker.ImageName:     fixture.ClientContainerImageName,
 			}).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
 			)),
 
 		fixture.ServerContainerNodeID: container(fixture.ServerContainerNodeID).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.ServerProcessNodeID,
 			)),
 
 		fixture.ServerContainer2NodeID: container(fixture.ServerContainer2NodeID),
@@ -194,12 +184,12 @@ var (
 				docker.ContainerHostname: fixture.ClientContainerHostname,
 			}).
 			AddCounter(report.Container, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
-				RenderedContainers[fixture.ClientContainerNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
+				fixture.ClientContainerNodeID,
 			)),
 
 		fixture.ServerContainerHostname: containerHostnameNode(fixture.ServerContainerHostname).
@@ -207,11 +197,11 @@ var (
 				docker.ContainerHostname: fixture.ServerContainerHostname,
 			}).
 			AddCounter(report.Container, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
-				RenderedContainers[fixture.ServerContainerNodeID],
-				RenderedContainers[fixture.ServerContainer2NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.ServerProcessNodeID,
+				fixture.ServerContainerNodeID,
+				fixture.ServerContainer2NodeID,
 			)),
 
 		uncontainedServerID:       uncontainedServerNode,
@@ -230,21 +220,21 @@ var (
 				docker.ImageName:  fixture.ClientContainerImageName,
 			}).
 			AddCounter(report.Container, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
-				RenderedContainers[fixture.ClientContainerNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
+				fixture.ClientContainerNodeID,
 			)),
 
 		ServerContainerImageNodeID: containerImage(ServerContainerImageNodeID).
 			AddCounter(report.Container, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
-				RenderedContainers[fixture.ServerContainerNodeID],
-				RenderedContainers[fixture.ServerContainer2NodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.ServerProcessNodeID,
+				fixture.ServerContainerNodeID,
+				fixture.ServerContainer2NodeID,
 			)),
 
 		uncontainedServerID:       uncontainedServerNode,
@@ -253,11 +243,11 @@ var (
 	}
 
 	UnmanagedServerID   = render.MakePseudoNodeID(render.UnmanagedID, fixture.ServerHostID)
-	unmanagedServerNode = pseudo(UnmanagedServerID, render.OutgoingInternetID).WithChildren(report.MakeNodeSet(
-		uncontainedServerNode,
-		RenderedEndpoints[fixture.NonContainerNodeID],
-		RenderedProcesses[fixture.NonContainerProcessNodeID],
-		RenderedContainers[fixture.ServerContainer2NodeID],
+	unmanagedServerNode = pseudo(UnmanagedServerID, render.OutgoingInternetID).WithChildren(report.MakeIDList(
+		uncontainedServerID,
+		fixture.NonContainerNodeID,
+		fixture.NonContainerProcessNodeID,
+		fixture.ServerContainer2NodeID,
 	)).
 		AddCounter(report.Container, 1).
 		AddCounter(render.Pseudo, 1)
@@ -265,20 +255,20 @@ var (
 	RenderedPods = report.Nodes{
 		fixture.ClientPodNodeID: pod(fixture.ClientPodNodeID, fixture.ServerPodNodeID).
 			AddCounter(report.Container, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
-				RenderedContainers[fixture.ClientContainerNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
+				fixture.ClientContainerNodeID,
 			)),
 
 		fixture.ServerPodNodeID: pod(fixture.ServerPodNodeID).
 			AddCounter(report.Container, 1).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
-				RenderedContainers[fixture.ServerContainerNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.ServerProcessNodeID,
+				fixture.ServerContainerNodeID,
 			)),
 
 		fixture.PersistentVolumeClaimNodeID: persistentVolumeClaim(fixture.PersistentVolumeClaimNodeID, fixture.PersistentVolumeNodeID).
@@ -289,7 +279,7 @@ var (
 				kubernetes.VolumeName:       "pongvolume",
 				kubernetes.AccessModes:      "ReadWriteOnce",
 				kubernetes.StorageClassName: "standard",
-			}).WithChild(report.MakeNode(fixture.PersistentVolumeNodeID).WithTopology(report.PersistentVolume)),
+			}).WithChildID(fixture.PersistentVolumeNodeID),
 
 		fixture.PersistentVolumeNodeID: persistentVolume(fixture.PersistentVolumeNodeID, fixture.VolumeSnapshotNodeID).
 			WithLatests(map[string]string{
@@ -300,13 +290,13 @@ var (
 				kubernetes.AccessModes:      "ReadWriteOnce",
 				kubernetes.StorageClassName: "standard",
 				kubernetes.StorageDriver:    "iSCSI",
-			}).WithChild(report.MakeNode(fixture.VolumeSnapshotNodeID).WithTopology(report.VolumeSnapshot)),
+			}).WithChildID(fixture.VolumeSnapshotNodeID),
 
 		fixture.StorageClassNodeID: StorageClass(fixture.StorageClassNodeID, fixture.PersistentVolumeClaimNodeID).
 			WithLatests(map[string]string{
 				kubernetes.Name:        "standard",
 				kubernetes.Provisioner: "pong",
-			}).WithChild(report.MakeNode(fixture.PersistentVolumeClaimNodeID).WithTopology(report.PersistentVolumeClaim)),
+			}).WithChildID(fixture.PersistentVolumeClaimNodeID),
 
 		fixture.VolumeSnapshotNodeID: volumeSnapshot(fixture.VolumeSnapshotNodeID, fixture.VolumeSnapshotDataNodeID).
 			WithLatests(map[string]string{
@@ -315,7 +305,7 @@ var (
 				kubernetes.VolumeClaim:  "pvc-6124",
 				kubernetes.SnapshotData: "vsd-1234",
 				kubernetes.VolumeName:   "pongvolume",
-			}).WithChild(report.MakeNode(fixture.VolumeSnapshotDataNodeID).WithTopology(report.VolumeSnapshotData)),
+			}).WithChildID(fixture.VolumeSnapshotDataNodeID),
 
 		fixture.VolumeSnapshotDataNodeID: volumeSnapshotData(fixture.VolumeSnapshotDataNodeID).
 			WithLatests(map[string]string{
@@ -332,17 +322,17 @@ var (
 	RenderedPodServices = report.Nodes{
 		fixture.ServiceNodeID: service(fixture.ServiceNodeID, fixture.ServiceNodeID).
 			AddCounter(report.Pod, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
-				RenderedContainers[fixture.ClientContainerNodeID],
-				RenderedContainers[fixture.ServerContainerNodeID],
-				RenderedPods[fixture.ClientPodNodeID],
-				RenderedPods[fixture.ServerPodNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.Server80NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
+				fixture.ServerProcessNodeID,
+				fixture.ClientContainerNodeID,
+				fixture.ServerContainerNodeID,
+				fixture.ClientPodNodeID,
+				fixture.ServerPodNodeID,
 			)),
 
 		UnmanagedServerID:         unmanagedServerNode,
@@ -359,14 +349,14 @@ var (
 			AddCounter(report.ContainerImage, 1).
 			AddCounter(report.Pod, 1).
 			AddCounter(report.Process, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Client54001NodeID],
-				RenderedEndpoints[fixture.Client54002NodeID],
-				RenderedProcesses[fixture.ClientProcess1NodeID],
-				RenderedProcesses[fixture.ClientProcess2NodeID],
-				RenderedContainers[fixture.ClientContainerNodeID],
-				RenderedContainerImages[ClientContainerImageNodeID],
-				RenderedPods[fixture.ClientPodNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Client54001NodeID,
+				fixture.Client54002NodeID,
+				fixture.ClientProcess1NodeID,
+				fixture.ClientProcess2NodeID,
+				fixture.ClientContainerNodeID,
+				ClientContainerImageNodeID,
+				fixture.ClientPodNodeID,
 			)),
 
 		fixture.ServerHostNodeID: hostNode(fixture.ServerHostNodeID, render.OutgoingInternetID).
@@ -374,15 +364,15 @@ var (
 			AddCounter(report.ContainerImage, 1).
 			AddCounter(report.Pod, 1).
 			AddCounter(report.Process, 2).
-			WithChildren(report.MakeNodeSet(
-				RenderedEndpoints[fixture.Server80NodeID],
-				RenderedEndpoints[fixture.NonContainerNodeID],
-				RenderedProcesses[fixture.ServerProcessNodeID],
-				RenderedProcesses[fixture.NonContainerProcessNodeID],
-				RenderedContainers[fixture.ServerContainerNodeID],
-				RenderedContainers[fixture.ServerContainer2NodeID],
-				RenderedContainerImages[ServerContainerImageNodeID],
-				RenderedPods[fixture.ServerPodNodeID],
+			WithChildren(report.MakeIDList(
+				fixture.Server80NodeID,
+				fixture.NonContainerNodeID,
+				fixture.ServerProcessNodeID,
+				fixture.NonContainerProcessNodeID,
+				fixture.ServerContainerNodeID,
+				fixture.ServerContainer2NodeID,
+				ServerContainerImageNodeID,
+				fixture.ServerPodNodeID,
 			)),
 
 		// due to https://github.com/weaveworks/scope/issues/1323 we are dropping
diff --git a/render/id.go b/render/id.go
index 72ca6feb9..68c358069 100644
--- a/render/id.go
+++ b/render/id.go
@@ -52,7 +52,7 @@ func ParseGroupNodeTopology(topology string) (string, string, bool) {
 
 // NewDerivedNode makes a node based on node, but with a new ID
 func NewDerivedNode(id string, node report.Node) report.Node {
-	return report.MakeNode(id).WithChildren(node.Children.Add(node))
+	return report.MakeNode(id).WithChildren(node.ChildIDs.Add(node.ID))
 }
 
 // NewDerivedPseudoNode makes a new pseudo node with the node as a child
diff --git a/render/metrics.go b/render/metrics.go
index 2658cdd44..2f8a46633 100644
--- a/render/metrics.go
+++ b/render/metrics.go
@@ -22,11 +22,13 @@ type propagateSingleMetrics struct {
 func (p propagateSingleMetrics) Render(ctx context.Context, rpt report.Report) Nodes {
 	nodes := p.r.Render(ctx, rpt)
 	outputs := make(report.Nodes, len(nodes.Nodes))
+	topology, _ := rpt.Topology(p.topology)
 	for id, n := range nodes.Nodes {
 		var first report.Node
 		found := 0
-		n.Children.ForEach(func(child report.Node) {
-			if child.Topology == p.topology {
+		for _, childID := range n.ChildIDs {
+			if ty, ok := report.NodeIDType(childID); ok && ty == p.topology {
+				child := topology.Nodes[childID]
 				if _, ok := child.Latest.Lookup(report.DoesNotMakeConnections); !ok {
 					if found == 0 {
 						first = child
@@ -34,7 +36,7 @@ func (p propagateSingleMetrics) Render(ctx context.Context, rpt report.Report) N
 					found++
 				}
 			}
-		})
+		}
 		if found == 1 {
 			n = n.WithMetrics(first.Metrics)
 		}
diff --git a/render/metrics_test.go b/render/metrics_test.go
index 5e6f74e31..9bb32ea81 100644
--- a/render/metrics_test.go
+++ b/render/metrics_test.go
@@ -13,6 +13,36 @@ import (
 
 func TestPropagateSingleMetrics(t *testing.T) {
 	now := time.Now()
+	empty := report.MakeNode("empty")
+	child1 := report.MakeNode(report.MakeContainerNodeID("child1")).
+		WithTopology(report.Container).
+		WithMetrics(report.Metrics{
+			"metric1": report.MakeMetric(nil),
+		})
+	child2 := report.MakeNode(report.MakeContainerNodeID("child2")).
+		WithTopology(report.Container).
+		WithMetrics(report.Metrics{
+			"metric2": report.MakeMetric(nil),
+		})
+	child2p := report.MakeNode(report.MakeProcessNodeID("host1", "child2")).
+		WithTopology("Process").
+		WithMetrics(report.Metrics{
+			"metric2": report.MakeMetric(nil),
+		})
+	pause := report.MakeNode(report.MakeContainerNodeID("pause")).
+		WithLatest(report.DoesNotMakeConnections, now, "").
+		WithTopology(report.Container).
+		WithMetrics(report.Metrics{
+			"metric2": report.MakeMetric(nil),
+		})
+	a := report.MakeNode("a").WithChildID(child1.ID)
+	rpt := report.MakeReport()
+	rpt.Container.AddNode(empty)
+	rpt.Container.AddNode(a)
+	rpt.Container.AddNode(child1)
+	rpt.Container.AddNode(child2)
+	rpt.Container.AddNode(pause)
+	rpt.Process.AddNode(child2p)
 	for _, c := range []struct {
 		name     string
 		input    report.Node
@@ -21,146 +51,50 @@ func TestPropagateSingleMetrics(t *testing.T) {
 	}{
 		{
 			name:     "empty",
-			input:    report.MakeNode("empty"),
+			input:    empty,
 			topology: "",
 			output:   report.Nodes{"empty": report.MakeNode("empty")},
 		},
 		{
-			name: "one child",
-			input: report.MakeNode("a").WithChildren(
-				report.MakeNodeSet(
-					report.MakeNode("child1").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric1": report.MakeMetric(nil),
-						}),
-				),
-			),
+			name:     "one child",
+			input:    a,
 			topology: report.Container,
 			output: report.Nodes{
 				"a": report.MakeNode("a").WithMetrics(report.Metrics{
 					"metric1": report.MakeMetric(nil),
-				}).WithChildren(
-					report.MakeNodeSet(
-						report.MakeNode("child1").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric1": report.MakeMetric(nil),
-							}),
-					),
-				),
+				}).WithChildID(child1.ID),
 			},
 		},
 		{
-			name: "ignores other topologies",
-			input: report.MakeNode("a").WithChildren(
-				report.MakeNodeSet(
-					report.MakeNode("child1").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric1": report.MakeMetric(nil),
-						}),
-					report.MakeNode("child2").
-						WithTopology("otherTopology").
-						WithMetrics(report.Metrics{
-							"metric2": report.MakeMetric(nil),
-						}),
-				),
-			),
+			name:     "ignores other topologies",
+			input:    report.MakeNode("a").WithChildren(report.MakeIDList(child1.ID, child2p.ID)),
 			topology: report.Container,
 			output: report.Nodes{
 				"a": report.MakeNode("a").WithMetrics(report.Metrics{
 					"metric1": report.MakeMetric(nil),
-				}).WithChildren(
-					report.MakeNodeSet(
-						report.MakeNode("child1").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric1": report.MakeMetric(nil),
-							}),
-						report.MakeNode("child2").
-							WithTopology("otherTopology").
-							WithMetrics(report.Metrics{
-								"metric2": report.MakeMetric(nil),
-							}),
-					),
-				),
+				}).WithChildren(report.MakeIDList(child1.ID, child2p.ID)),
 			},
 		},
 		{
-			name: "two children",
-			input: report.MakeNode("a").WithChildren(
-				report.MakeNodeSet(
-					report.MakeNode("child1").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric1": report.MakeMetric(nil),
-						}),
-					report.MakeNode("child2").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric2": report.MakeMetric(nil),
-						}),
-				),
-			),
+			name:     "two children",
+			input:    report.MakeNode("a").WithChildren(report.MakeIDList(child1.ID, child2.ID)),
 			topology: report.Container,
 			output: report.Nodes{
-				"a": report.MakeNode("a").WithChildren(
-					report.MakeNodeSet(
-						report.MakeNode("child1").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric1": report.MakeMetric(nil),
-							}),
-						report.MakeNode("child2").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric2": report.MakeMetric(nil),
-							}),
-					),
-				),
+				"a": report.MakeNode("a").WithChildren(report.MakeIDList(child1.ID, child2.ID)),
 			},
 		},
 		{
-			name: "ignores k8s pause container",
-			input: report.MakeNode("a").WithChildren(
-				report.MakeNodeSet(
-					report.MakeNode("child1").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric1": report.MakeMetric(nil),
-						}),
-					report.MakeNode("child2").
-						WithLatest(report.DoesNotMakeConnections, now, "").
-						WithTopology(report.Container).
-						WithMetrics(report.Metrics{
-							"metric2": report.MakeMetric(nil),
-						}),
-				),
-			),
+			name:     "ignores k8s pause container",
+			input:    report.MakeNode("a").WithChildren(report.MakeIDList(child1.ID, pause.ID)),
 			topology: report.Container,
 			output: report.Nodes{
 				"a": report.MakeNode("a").WithMetrics(report.Metrics{
 					"metric1": report.MakeMetric(nil),
-				}).WithChildren(
-					report.MakeNodeSet(
-						report.MakeNode("child1").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric1": report.MakeMetric(nil),
-							}),
-						report.MakeNode("child2").
-							WithLatest(report.DoesNotMakeConnections, now, "").
-							WithTopology(report.Container).
-							WithMetrics(report.Metrics{
-								"metric2": report.MakeMetric(nil),
-							}),
-					),
-				),
+				}).WithChildren(report.MakeIDList(child1.ID, pause.ID)),
 			},
 		},
 	} {
-		got := render.PropagateSingleMetrics(c.topology, mockRenderer{report.Nodes{c.input.ID: c.input}}).Render(context.Background(), report.Report{}).Nodes
+		got := render.PropagateSingleMetrics(c.topology, mockRenderer{report.Nodes{c.input.ID: c.input}}).Render(context.Background(), rpt).Nodes
 		if !reflect.DeepEqual(got, c.output) {
 			t.Errorf("[%s] Diff: %s", c.name, test.Diff(c.output, got))
 		}
diff --git a/render/persistentvolume.go b/render/persistentvolume.go
index 8c9b281f4..ebe947271 100644
--- a/render/persistentvolume.go
+++ b/render/persistentvolume.go
@@ -33,7 +33,7 @@ func (v volumesRenderer) Render(ctx context.Context, rpt report.Report) Nodes {
 			volumeName, _ := p.Latest.Lookup(report.KubernetesName)
 			if volume == volumeName {
 				n.Adjacency = n.Adjacency.Add(p.ID)
-				n.Children = n.Children.Add(p)
+				n = n.WithChildID(p.ID)
 			}
 		}
 		nodes[id] = n
@@ -65,7 +65,7 @@ func (v podToVolumesRenderer) Render(ctx context.Context, rpt report.Report) Nod
 				pvcNamespace, _ := pvcNode.Latest.Lookup(report.KubernetesNamespace)
 				if (pvcName == ClaimName) && (podNamespace == pvcNamespace) {
 					podNode.Adjacency = podNode.Adjacency.Add(pvcNode.ID)
-					podNode.Children = podNode.Children.Add(pvcNode)
+					podNode = podNode.WithChildID(pvcNode.ID)
 					break
 				}
 			}
@@ -91,7 +91,7 @@ func (v pvcToStorageClassRenderer) Render(ctx context.Context, rpt report.Report
 			storageClassName, _ := pvcNode.Latest.Lookup(report.KubernetesStorageClassName)
 			if storageClassName == storageClass {
 				scNode.Adjacency = scNode.Adjacency.Add(pvcNode.ID)
-				scNode.Children = scNode.Children.Add(pvcNode)
+				scNode = scNode.WithChildID(pvcNode.ID)
 			}
 		}
 		nodes[scID] = scNode
@@ -114,7 +114,7 @@ func (v pvToSnapshotRenderer) Render(ctx context.Context, rpt report.Report) Nod
 			snapshotPVName, _ := volumeSnapshotNode.Latest.Lookup(report.KubernetesVolumeName)
 			if volumeName == snapshotPVName {
 				p.Adjacency = p.Adjacency.Add(volumeSnapshotNode.ID)
-				p.Children = p.Children.Add(volumeSnapshotNode)
+				p = p.WithChildID(volumeSnapshotNode.ID)
 			}
 		}
 		nodes[pvNodeID] = p
@@ -138,7 +138,7 @@ func (v volumeSnapshotRenderer) Render(ctx context.Context, rpt report.Report) N
 			snapshotDataName, _ := volumeSnapshotDataNode.Latest.Lookup(report.KubernetesName)
 			if snapshotDataName == snapshotData {
 				volumeSnapshotNode.Adjacency = volumeSnapshotNode.Adjacency.Add(volumeSnapshotDataNode.ID)
-				volumeSnapshotNode.Children = volumeSnapshotNode.Children.Add(volumeSnapshotDataNode)
+				volumeSnapshotNode = volumeSnapshotNode.WithChildID(volumeSnapshotDataNode.ID)
 			}
 			nodes[volumeSnapshotDataID] = volumeSnapshotDataNode
 		}
diff --git a/render/render.go b/render/render.go
index 4327277de..38d6d684a 100644
--- a/render/render.go
+++ b/render/render.go
@@ -161,8 +161,7 @@ type joinResults struct {
 func newJoinResults(inputNodes report.Nodes) joinResults {
 	nodes := make(report.Nodes, len(inputNodes))
 	for id, n := range inputNodes {
-		n.Adjacency = nil              // result() assumes all nodes start with no adjacencies
-		n.Children = n.Children.Copy() // so we can do unsafe adds
+		n.Adjacency = nil // result() assumes all nodes start with no adjacencies
 		nodes[id] = n
 	}
 	return joinResults{nodes: nodes, mapped: map[string]string{}, multi: map[string][]string{}}
@@ -193,7 +192,7 @@ func (ret *joinResults) addUnmappedChild(m report.Node, id string, topology stri
 	if !exists {
 		result = report.MakeNode(id).WithTopology(topology)
 	}
-	result.Children.UnsafeAdd(m)
+	result = result.WithChildID(m.ID)
 	if m.Topology != report.Endpoint { // optimisation: we never look at endpoint counts
 		result = result.AddCounter(m.Topology, 1)
 	}
@@ -212,7 +211,7 @@ func (ret *joinResults) addChild(m report.Node, id string, topology string) {
 func (ret *joinResults) addChildAndChildren(m report.Node, id string, topology string) {
 	ret.addUnmappedChild(m, id, topology)
 	result := ret.nodes[id]
-	result.Children.UnsafeMerge(m.Children)
+	result = result.WithChildren(m.ChildIDs)
 	ret.nodes[id] = result
 	ret.mapChild(m.ID, id)
 }
@@ -221,7 +220,6 @@ func (ret *joinResults) addChildAndChildren(m report.Node, id string, topology s
 func (ret *joinResults) passThrough(n report.Node) {
 	n.Adjacency = nil // result() assumes all nodes start with no adjacencies
 	ret.nodes[n.ID] = n
-	n.Children = n.Children.Copy() // so we can do unsafe adds
 	ret.mapChild(n.ID, n.ID)
 }
 
diff --git a/report/id.go b/report/id.go
index 37db28df1..436b02b9b 100644
--- a/report/id.go
+++ b/report/id.go
@@ -262,6 +262,19 @@ func split2(s, sep string) (s1, s2 string, ok bool) {
 	return s[:pos], s[pos+1:], true
 }
 
+// NodeIDType returns the type of a node ID - e.g. process, pod, endpoint
+func NodeIDType(nodeID string) (string, bool) {
+	if _, tag, ok := ParseNodeID(nodeID); ok {
+		switch {
+		case len(tag) >= 2 && tag[0] == '<' && tag[len(tag)-1] == '>':
+			return tag[1 : len(tag)-1], true
+		case len(tag) >= 1 && tag[0] >= '0' && tag[0] <= '9':
+			return Endpoint, true
+		}
+	}
+	return "", false
+}
+
 // ParseNodeID produces the id and tag of a single-component node ID.
 func ParseNodeID(nodeID string) (id string, tag string, ok bool) {
 	return split2(nodeID, ScopeDelim)
diff --git a/report/id_test.go b/report/id_test.go
index f6306e5c1..bbe0fb1ef 100644
--- a/report/id_test.go
+++ b/report/id_test.go
@@ -3,6 +3,7 @@ package report_test
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/weaveworks/scope/report"
 )
 
@@ -78,3 +79,18 @@ func TestECSServiceNodeIDCompat(t *testing.T) {
 		t.Errorf("Backwards-compatible id %q parsed name to %q, expected %q", testID, name, testName)
 	}
 }
+
+func TestNodeIDType(t *testing.T) {
+	ty, ok := report.NodeIDType("")
+	assert.False(t, ok)
+	ty, ok = report.NodeIDType(clientHostNodeID)
+	assert.True(t, ok)
+	assert.Equal(t, report.Host, ty)
+	ty, ok = report.NodeIDType(client54001EndpointNodeID)
+	assert.True(t, ok)
+	assert.Equal(t, report.Endpoint, ty)
+	rsetID := report.MakeReplicaSetNodeID("foo")
+	ty, ok = report.NodeIDType(rsetID)
+	assert.True(t, ok)
+	assert.Equal(t, report.ReplicaSet, ty)
+}
diff --git a/report/node.go b/report/node.go
index 859398be0..5dd52d7b0 100644
--- a/report/node.go
+++ b/report/node.go
@@ -19,7 +19,7 @@ type Node struct {
 	Latest    StringLatestMap `json:"latest,omitempty"`
 	Metrics   Metrics         `json:"metrics,omitempty" deepequal:"nil==empty"`
 	Parents   Sets            `json:"parents,omitempty"`
-	Children  NodeSet         `json:"children,omitempty"`
+	ChildIDs  IDList          `json:"cs,omitempty"`
 }
 
 // MakeNode creates a new Node with no initial metadata.
@@ -162,14 +162,16 @@ func (n Node) PruneParents() Node {
 }
 
 // WithChildren returns a fresh copy of n, with children merged in.
-func (n Node) WithChildren(children NodeSet) Node {
-	n.Children = n.Children.Merge(children)
+func (n Node) WithChildren(children IDList) Node {
+	for _, childID := range children {
+		n.ChildIDs = n.ChildIDs.Add(childID)
+	}
 	return n
 }
 
-// WithChild returns a fresh copy of n, with one child merged in.
-func (n Node) WithChild(child Node) Node {
-	n.Children = n.Children.Merge(MakeNodeSet(child))
+// WithChildID returns a fresh copy of n, with one child merged in.
+func (n Node) WithChildID(childID string) Node {
+	n.ChildIDs = n.ChildIDs.Add(childID)
 	return n
 }
 
@@ -194,7 +196,7 @@ func (n Node) Merge(other Node) Node {
 		Latest:    n.Latest.Merge(other.Latest),
 		Metrics:   n.Metrics.Merge(other.Metrics),
 		Parents:   n.Parents.Merge(other.Parents),
-		Children:  n.Children.Merge(other.Children),
+		ChildIDs:  n.ChildIDs.Merge(other.ChildIDs),
 	}
 }
 
diff --git a/test/utils/prune.go b/test/utils/prune.go
index 69860e913..6be1dbdcd 100644
--- a/test/utils/prune.go
+++ b/test/utils/prune.go
@@ -21,15 +21,11 @@ func Prune(nodes report.Nodes) report.Nodes {
 // necessary for rendering nodes and edges stripped away. Specifically, that
 // means cutting out parts of the Node.
 func PruneNode(node report.Node) report.Node {
-	prunedChildren := report.MakeNodeSet()
-	node.Children.ForEach(func(child report.Node) {
-		prunedChildren = prunedChildren.Add(PruneNode(child))
-	})
 	prunedNode := report.MakeNode(
 		node.ID).
 		WithTopology(node.Topology).
 		WithAdjacent(node.Adjacency...).
-		WithChildren(prunedChildren)
+		WithChildren(node.ChildIDs)
 	// Copy counters across, but with zero timestamp so they compare equal
 	node.Latest.ForEach(func(k string, _ time.Time, v string) {
 		if strings.HasPrefix(k, report.CounterPrefix) {