Mitosis divides the nucleus of a cell into two new nuclei.

The first stage of mitosis is prophase. Here we see the DNA has wrapped tightly around proteins to form chromosomes, the nucleolus disappears, and microtubules begin to grow out from the centrosomes.

The next stage is prometaphase where the nuclear membrane breaks down.

In prometaphase, the microtubules also lengthen by the addition of tubulin proteins to the growing end. The microtubules then attach to the chromosomes at the kinetochore--a protein complex located at the centromere of each chromosome.

In metaphase, the chromosomes align at the equator of the cell.

In anaphase, the sister chromatids are separated. The separation occurs when the microtubules connected to the chromatids shorten by the loss of tubulin.

Also, the microtubules not connected to the chromatids lengthen to push the two poles of the cell apart.

In telophase, the spindle apparatus made up of microtubules breaks down.

After the spindle apparatus breaks down, the nuclear membrane reforms, and the chromosome uncoil.

Finally, at the end of telophase, the nucleolus reappears. Mitosis is now complete.