Each human being is made up of up to 100 billion (!) cells. Each of them originates from one single fertilized ovum. In order for the body to be able to grow, new cells are generated all the time.

Even in adults, old cells of the body are replaced by new ones each second. Because our skin is permanently renewed, marker stripes that cannot be removed by washing vanish within a few days. Muscles grow when we exercise, and they shrink when we become lazy and inactive. And if blood cells did not have the ability to divide, it would be impossible to donate blood.

Cells proliferate through cell division.