Cell Death and a little science humor
This is quite literally what goes on every day in all of us. We are made of trillions of cells, and these cells are constantly undergoing quality control and checkups. By some estimates, 50-70 billion cells undergo programmed cell death (Apoptosis) every day. It is very important to understand that we are all constantly dying and being re-made, and apoptosis is essential to maintaining healthy tissues. It is when this equilibrium is perturbed that cancers can arise, and when cancers can spread and metastasize.
Admittedly, I am a bit biased, as this area of cell biology is very near to my heart. (See Research)