Mitosis. Illustration of the cell cycle with stages of mitosis (nuclear division) and cytokinesis (cell division). Between periods of division the cell enters a stage called interphase (top). Early in mitosis, during prophase, chromosomes (red) condense. Each chromosome has replicated and is composed of two sister chromatids. The nuclear envelope (blue) disintegrates during prometaphase (left) and the chromosomes line up along the centre of the cell (metaphase, lower left). Microtubules (black) attach to the chromosomes and pull them apart to opposite poles of the cell (anaphase, bottom). Two nuclei form and the cell begins to divide during telophase (lower right). This process is completed during cytokinesis to form two identical daughter cells (upper right).