Cell division. Time-exposure light micrograph showing the different stages in mitosis and cytokinesis (nuclear and cellular division, respectively). At top left the cells are in prophase, the chromosomes, made of deoxyribonucleic acid (DNA) are condensed and clear. The second line shows metaphase, with the chromosomes lining up along the left-hand side of the cell. The third line is anaphase, the chromosomes are being pulled apart to opposite poles of the cell. The fourth line shows telophase, during which the nuclear envelope reforms and the cell begins to divide into two. This process is completed during cytokinesis (bottom line) to form two daughter cells.