Anyone who’s seen an episode of Masters of Sex knows that without the heart-racing, heavy-breathing prequel that encompasses foreplay and arousal, your chances of orgasm from penetrative sex are pretty slim. (Seriously, it’s science.) According to a study in the Journal of Sexual Research, both men and women hope to engage in foreplay for about 20 minutes before beginning intercourse — and yet, most report that actual foreplay only lasts about half that time.Sure, there are some great hookups that go from zero to 60 in about as many seconds. It’s all good as long as you’re really, truly turned-on before going all the way. Why is that? And, what does it take to get there? And, what’s actually happening — between your legs as well as between your ears — during arousal? We combed through the research to figure out the science behind getting turned on. Because, although there are a lot of things we cut corners on to save time (hi, teeth-brushing for only 30 seconds) foreplay shouldn’t be one of them.