Mitosis (Definition, Diagram & Stages Of Mitosis) - BYJUS Mitosis is the phase of the cell cycle where the nucleus of a cell is divided into two nuclei with an equal amount of genetic material in both the daughter nuclei. It succeeds the G2 phase and is succeeded by cytoplasmic division after the separation of the nucleus. Mitosis is essential for the growth of the cells and the replacement of worn-out cells.