Cell division is a multistage reorganization of morphology in which alterations of cytoskeleton play the central role. Division, like reorganization of interphase cells, described in Chapter 7, is based on alteration of the assembly and distribution of cytoskeletal structures. There are, however, important differences between these two types of reorganization. Morphogenetic reorganization adapts the morphology of the interphase cell to its environment; the course of this reorganization is directed by external factors. In contrast, the course of cell division is directed by a strict internal program; external factors can only disturb this course.