Mitosis is when a cell reproduces itself by splitting to form two identical offspring.
In a cell thats not dividing, the DNA is all spread out in long strings. If the cell gets a signal to divide it duplicates its DNA, so there is a new copy for each new cell. They then line up at the centre and cell fibres pull them apart. Membraes form around each of the sets of chromosomes. These become the nuclei of the 2 new cless. It then divides. You have 2 new cells, containing exactly the same DNA- theyre identical.