‘Morphogenesis’ describes the changing shape of animal embryos during their early development, which principally occurs during gastrulation, where a two-dimensional sheet of cells is transformed into the complex three-dimensional animal body, and involves extensive rearrangements of cell layers and the directed movement of cells from one location to another. The key cellular properties involved in changes in animal embryonic form are cell contraction, cell adhesiveness, and cell division. In plants there is no cell movement or change in shape. Changes in form are generated by oriented cell division and cell expansion. Directed dilation is an important force in plants and results from an increase in hydrostatic pressure inside a cell.