Figure 4.

Tissue tectonics. Three snapshots in time are shown in this schematic, at time points t1, t2 and t3. Two populations of cells are shown in orange and teal, each of which is found in different tissue sheets. As the tissues slide relative to one another, the populations of interest come into close apposition, allowing intercellular signalling to occur. At t3, the inductive signalling event has occurred and both populations' cells have experienced a change in cell state. Clearly, tissue tectonics is an important contributor to the timing of signalling events in development.