The 6 phases of the cell cycle (from top left) are shown for 2 cells in the embryo of the marine worm Cerebratulus marginatus. Each image is a projection of a 40-80 0.3-μm confocal section: interphase, microtubules are long and diffuse; prophase, chromosomes condense and small asters appear; prometaphase, the nuclear envelope breaks down but the spindle is not yet built; metaphase, chromosomes aligned at the spindle equator; anaphase, sister chromatids separate along the spindle as astral microtubules grow; telophase, cleavage furrow constricts around astral microtubules and the central spindle as 2 nuclei reassemble.

By George von Dassow, University of Oregon

look mitosis and meiosis! xD