Differential interference contrast (DIC) light micrograph of onion (Allium cepa) meristematic cells undergoing mitosis (nuclear division). Mitosis is the formation of two daughter nuclei from one parent nucleus. The cell at centre and the cells to the upper right and left of it are in different stages of anaphase of mitosis. At anaphase sister chromatids, which are made of DNA (deoxyribonucleic acid, red), are moved to separate poles by spindles (not seen). Two identical chromatids make up one chromosome, so each cell retains a copy of the parent cell's genetic information. At centre left and bottom right the cells are in telophase, the last stage of mitosis before cytokinesis (cellular division). Orcein staining.