Cell interfaces change behavior, leading to multiple rounds of intercalation. (A) Counts of interface changes over time. Each subgraph represents a time period that cells are visible during germband extension (red: contraction; blue: elongation). (n = 726 cells, k = 3 embryos). (B) Sample images at different time points of a cell that has five contracting interfaces and three elongating interfaces. Scale bars = 5 µm. (C) Still image of the start of germband extension with contracting interfaces highlighted to indicate the time period until the interface contracts. (D) Initial interface orientation angle versus timepoint of the higher-order vertex configuration, color-coded by initial contraction/elongation rates (n = 129 interfaces, k = 6 embryos).