For any biologists, or biology-adjacent professionals around, what's something you've enjoyed studying but rarely find opportunities to discuss?

The complement cascade

I do (or did - I sold out) theoretical biology, so basically everything. Multilevel selection theory was probably my favorite because it incorporates everything from network theory to emergent behaviors and evolutionary dynamics.

I do get to discuss it, though. I developed a reputation for going out to bars and explaining it to people who were a couple of pints in and were probably very confused but too polite to simply walk away.