Dividing pollen cell. Coloured scanning electron micrograph of a section through a pollen mother cell from a spiderwort (Tradescantia reflexa) flower, during the metaphase (I) stage of meiosis (gamete formation) - showing: chromosomes (yellow), spindle fibres (green), cytoplasm (violet) and the cell wall (blue). During meiosis four daughter nuclei are formed from one parent nucleus after two stages of nuclear division. Meiosis occurs only in the sex cells (gametes). At metaphase (I) pairs of homologous chromosomes line up along the centre of the cell ready to be separated during anaphase (I). Separation results in two cells with half the usual number of chromosomes. The full complement is restored when two gametes fuse during fertilisation.