Mitosis. Immunofluorescence light micrograph of two cells during prophase (lower left) and metaphase (centre right) of mitosis (nuclear division). During mitosis two daughter nuclei are formed from one parent nucleus. During prophase, chromosomes (purple) condense into defined units, allowing organised and equal segregation into daughter nuclei. Also the nuclear envelope breaks down, allowing microtubules (green) to interact with the chromosomes. During metaphase the chromosomes line up along the centre of the cell and the microtubules attach to them. Chromosomes are made up of two identical chromatids, which are pulled to opposite poles of the cell by the microtubules.