Cell division. Fluorescent micrograph of two animal cells during cytokinesis (cell division). Cytokinesis occurs after nuclear division (mitosis), which produces two daughter nuclei (black) containing deoxyribonucleic acid (DNA, yellow). A contractile ring made of actin filaments forms beneath the cells plasma membrane. This contracts, creating a furrow in the cytoplasm (light blue). The furrow deepens, separating the cytoplasm and cell organelles, until the two new cells are formed. The dark blue structures are microtubules, part of the cell's cytoskeleton, along with the actin filaments. They separate the chromosomes during mitosis.