In the "resting" phase the chromosomes are not obvious within the nucleus.

Just before cell division starts, a lot of metabolic activity occurs, the chromosomes start to gradually shorten and thicken.

Each chromosome has divided to produce 2 identical chromatids, joined at a structure called the centromere. They begin to move towards the equator of the cell.

Once at the equator of the cell, the centromeres attach to threads of a spindle structure that has formed. (The spindle spans from one end of the cell to the other).

Contraction of the spindle fibres begins to cause the chromatids to pull apart from one another and move towards opposite ends of the cell.

The chromatids separate further. Energy for this is provided by mitochondria.

A new nuclear membrane begins to form round the 2 groups of chromatids. A new cell wall begins to be laid down.

The chromosomes begin to lengthen and uncoil.

Two new cells, identical to each other and to the parent cell. The cells now grow to full size.