I've studied lots of things!
First off, I have a 2 Bachelors degrees, one in Computer Science and the other in Physics.
In Physics my main interests were Quantum Computing, but I also studied Quantum Mechanics, Condensed Matter Physics and General Relativity
In Computer Science my main interest was Algorithms, but I also studied programming languages, theoretical computing and Design.
I've also studied simulations, especially biological ones, as well as Neural networks, Discrete Mathematics, Calculus, Linear Algebra and Vector Calculus.
My overall number one interest of study though would be Quantum Computing.