“Dopamine is involved in what experts call the 'sensations of reward area of the brain.' This makes us feel intense desire that can lead to feelings of euphoria, insomnia and loss of appetite, and it is only one actor in the great chemical ballet happening in our bodies,” Kirshenbaum writes. 

She says that some pretty amazing physical changes occur when we kiss someone we desire. Sure, our faces grow warm as our hearts beat out of our chests. But did you know that blood vessels dilate, too? 

And it doesn’t stop there. The pupils expand, which may explain why we have a tendency to close our eyes during a kiss. 

Even the nose gets in on the action. When a partner’s DNA is compatible with ours, his or her “scent” (yes, we all have a scent) helps to drive that craving for more. This, Kirshenbaum says, is why “there’s more to a kiss than meets the lips.”

All kissing aside, let’s get to business. After all, we often wonder what really happens when we hit a “home run.” 

What About Sex?

As it turns out, sex is like a drug, too. According to Health magazine, sex releases that infamous dopamine. So really, when we have sex, we’re drugged out on passion. 

"Taking cocaine and having sex don't feel exactly the same, but they do involve the same [brain] regions as well as different regions of the brain," Timothy Fong, M.D., associate professor of psychiatry at UCLA's David Geffen School of Medicine, tells Health. 

Plus, sex calms us down. There’s good reason why we often feel like sex is a stress buster, and research proves it.