If you had the time and opportunity to sit in on any college classes just for the purpose of learning about the subject, which classes would you choose? Why?

If I could sit in on any college class just to learn about the subject it would have be health classes. I would choose health because I would like to learn more about the human body and how things work. Honestly I don't think I know that much in detail about health and how things work. I just think it's interesting how things work in our bodies, and would like to learn more.