Color enhanced transmission electron micrograph showing mitosis. Midbody microtubules. No magnification given. Mitosis, the usual method of cell division, characterized typically by the resolving of the chromatin of the nucleus into a threadlike form, which condenses into chromosomes, each of which separates longitudinally into two parts, one part of each chromosome being retained in each of two new cells resulting from the original cell. The four main phases of mitosis are prophase, metaphase, anaphase, and telophase. Microtubule a hollow cylindrical structure in the cytoplasm of most cells, involved in intracellular shape and transport.