Figure 4: Neighbour exchange and its association of cluster internal cell extensions.

(a) Two incidences of neighbourhood exchange in a movie. The light blue cell (represented here by its nucleus), whose movement is indicated by the red dotted arrow at t=1.7 m, penetrates between the green and magenta cells, indicated by the yellow arrows at t=1.7 m and t=13.7 m, within ∼10 m. The gold cell, whose path is indicated by the blue dotted arrow, has similar behaviour and moves between the two green cells indicated by the white arrows. (Supplementary Movie 6). (b,c) The temporal topology change metric of two clusters, running and rotating respectively, without neighbour exchange. The reconstructed movies are shown in Supplementary Movie 7 and 8, respectively. (d) The temporal topology change metric of a cluster with four neighbour exchanges. The reconstructed movies are shown in Supplementary Movie 6. The x axis of hot peaks indicates the time points of such incidences occurring. The y axis indicates how long this neighbour exchange will take in min.