cytokinesis, in biology, the process by which one cell physically divides into two cells. Cytokinesis represents the major reproductive procedure of unicellular organisms, and it occurs in the process of embryonic development and tissue growth and repair of higher plants and animals. It generally follows nuclear doubling, whether in mitosis or in meiosis. Prokaryotes reproduce principally by binary fission, in which the mother cell enlarges until it divides into two identical daughter cells, with cytokinesis representing the physical division into the two daughter cells.
In animal cells cytokinesis is achieved through the constriction of the cell by a ring of contractile microfilaments consisting of actin and myosin, the proteins involved in muscle contraction and other forms of cell movement. In plant cells the cytoplasm is divided by the formation of a new cell wall, called the cell plate, between the two daughter cells. Once the daughter cells are separated, cellulose synthesis begins, and the cell plate becomes a primary cell wall.