Prophase cell division. Coloured transmission electron micrograph (TEM) of a section through a HeLa cell during prophase cell division (mitosis). At centre, the large granular nucleus of the cell is seen. Red regions in the nucleus are chromosomes which have condensed. This chromosomal process occurs at the prophase stage of cell division, in preparation for nuclear division. The nuclear membrane also disappears at this stage, although it is still visible here. During mitosis a cell produces two genetically identical daughter cells. HeLa cells are human cancer cells cultured in the laboratory and used in cancer research. Magnification: x2200 at 6x4.5cm size.