Mitosis is the division of the and begins with a stage called . As the nuclear envelope finishes dissolving, the cells enter , where microtubules from the spindle attach to the duplicated X-shaped chromosomes. When all chromosomes are fully attached to the spindle, they align at the midplate between poles. This marks the middle of mitosis, which is . As sister chromatids separate, cells enter and they finish separating and a nucleus reforms around each set of new chromosomes in . During this phase, cytokinesis also becomes visible as the cells themselves begin to divide.