Many experts recommend that adults learn how to masturbate for a whole host of reasons: it helps you learn about your own body, it means you don't have to rely on a partner for sexual stimulation and orgasm, and it has a reputation for being a stress-buster and general health boost. It's also cool if you don't masturbate, of course; not masturbating is also perfectly normal and healthy, so don't feel as if you're being left behind while everybody else runs around on the Touching Themselves Train. But what's actually happening in your body and your brain while you're stimulating yourself? And is it substantively different than what goes on when you have sex with a partner? Masturbation has had a particularly difficult reputation over the years; humans have been warned away from it by threats of hairy palms, madness and going blind.