Differential interference contrast (DIC) light micrograph of onion (Allium cepa) meristematic cells during mitosis (nuclear division). Mitosis is the formation of two daughter nuclei from one parent nucleus. At top left the cell is in interphase. The nucleus (round, centre) is clearly visible. As the cell moves into prophase (top centre), the nuclear envelope dissolves and the chromosomes (red) condense. The cell progress through prometaphase (top right) to metaphase (bottom left), where the chromosomes align along the centre of the cell. The chromosomes start to move to the opposite poles, guided by microtubules, during anaphase (bottom centre). At bottom right, the cell is in telophase. The separated chromosomes have moved to opposite ends of the cell and two new nuclei form around them. Orcein staining.