Secondly: Math

Math is hard if you don't know what you're doing, but it's beautiful if you do. And the transition from not knowing math to knowing math gives a feeling of accomplishment, dare I say elation. Ok, fine, I'm a nerd/geek/spaz/wedgie magnet, but it's true at all levels of mathematics, from elementary school to research. The ability to know a theory well enough to apply it to a variety of different situations is. from my perspective, a very human characteristic. Of course, every animal is doing an enormous number of calculations to perform any sort of movement, but humans are the only ones to have consciously elucidated a small fraction of the calculations that occur in our brains at every moment. And that's why I love it, it pulls the shroud off of many aspects of the world.

Yeah neuroscience is cool too, but no one concretely knows whats going on. And from what I've seen, biologists tend to dismiss the many worlds interpretation of quantum mechanics, which causes a splitting of universes at every decision point, and I'm a huge fan of it. Not to say that anything in science is concrete, but mathematics has been around long enough that the community is capable of filtering out any b.s. that arises.