Mitosis. Image 1 of 6. Coloured scanning electron micrograph (SEM) of the surface of a breast cancer cell during prophase, the first stage of mitotic cell division. During mitosis, the nuclear material of a cell divides, followed by separation of the cytoplasm and cell organelles to form two daughter cells. During prophase, which occurs after the nuclear material has already replicated, the chromosomes condense and the nuclear envelope dissolves. A proteinaceous spindle forms in the centre of the cell, along which the chromosomes pair up. Magnification: around x2200 when printed 10cm wide. For a sequence of mitosis, see images P672/088 to P672/093.