Apoptosis
Apoptosis is the controlled death of a cell. It is an important part of tissue development. For example, during limb development in a foetus, apoptosis allows digits (fingers and toes) to separate from each other. The process is quite common until puberty begins. Apoptosis is a  regulated and controlled process which works throughout an organism's life cycle. The rate of apoptosis is balanced by the rate of cell production by mitosis.