In this electron micrograph of a cell, the cleavage furrow has nearly completely divided the cell.
In cell biology, the cleavage furrow is the indentation that begins the process of cleavage, by which animal and some algalcells undergo cytokinesis. The same proteins responsible for muscle contraction, actin and myosin, begin the process of forming the cleavage furrow. Plant cells do not form a cleavage furrow. Instead, plant cells begin cytokinesis with the formation of a cell plate. The cleavage furrow begins on the outside of the cell and moves inward towards the center while the cell plate begins in the center and grows outward to meet the cell wall.
