So you want to be an intelligence analyst. Students occasionally write to me and ask for advice on getting a job in the Intelligence Community. (I became an intelligence analyst at DIA after undergrad. I was there for about three years, and after that, I did a few years of consulting for various intel agencies.) The below is a gist of that advice. It is heavily biased by my own experience, and none of the below is meant to be universal.
Apoptosis, or programmed cell death, is a naturally occurring process in the body. It involves a controlled sequence of steps in which cells signal self termination. Apoptosis works to keep the body's natural cell division process of mitosis in check.
As our brains develop, the body creates millions more cells than it needs; the ones that don't form synaptic connections undergo apoptosis so that the remaining cells function well. Programmed cell death is also necessary to start the process of menstruation. That's not to say that apoptosis is a perfect process. Sometimes, the wrong cells kill themselves off, and sometimes, the ones that should say auf Wiedersehen stick around instead.