Back when I was a pre-med, my first summer research internship was in a cancer lab. After a couple of weeks of cell culture and autoclaving stuff, they let me start working with the mice. They were inducing lung cancer in them to test some novel compound that was supposed to cure the cancer. Every day, I'd have to go to the mice room, swap in fresh water and food, and then bag all the dead mice individually in rubber gloves, and leave them on my supervisor's desk. Really opened my eyes.