To revive the original question, the part of science that interests me most is physics, and specifically that area in the overlap of astrophysics and particle physics where people are working on the origins and structure of the universe. When I was at school and university, the impression I got (probably wrongly) was that this was all settled: we understood the Standard Model and the Big Bang, and that seemed to cover everything. When I got interested in all this again, ten or twelve years ago, I discovered we knew more, and understood less (!). We had found, or were finding, the evidence for dark matter and dark energy, but there's no framework of theory to fit them into. To me, it feels rather like the state of physics in about 1900: lots of unexplained phenomena, waiting for relativity and quantum theory to tie it all together.
I probably should be interested in genetics, because it seems very likely that a lot of world-changing stuff is going to come out of it, but the biological side of science never really appealed to me (too descriptive, not enough logic and principles), and I stopped studying it at age 16.
It's not a science, but I'm very much interested in maths, particularly the intersection of group theory and geometry where things called polytopes live.