It was lightly raining in New York City that night. My heart was beating fast as he gently took my face in his hands. With a heated gaze, he pulled me close with a clear sense of purpose and desire. When our lips touched, it felt like everything began to move slow motion—the people, the cars, and the sounds of the city faded into the background until I was completely lost in the moment. Tender and romantic, yet intensely passionate at the same time—nothing ever felt more perfect.

If my life was a highlight reel of incredible moments, that kiss would make my top five. But what was it that truly made this kiss memorable? While I’ve secretly always dreamed of my own romantic kiss-in-the-rain movie moment, I knew it was something more than that.

Kissing is a uniquely human behavior, so it’s no wonder we’re perpetually fascinated by it and the feelings and sensations it produces. It’s the climax of our favorite love stories and the moment we’re always waiting for in movies. To Have and Have Not, Gone With the Wind, and The Notebook transcend time with kisses that captured our hearts. Here is the science behind these famous on-screen smooches along with a few other surprising facts:

To Have and Have Not

In the classic 1944 movie To Have and Have Not, starring on-screen power couple Lauren Bacall and Humphrey Bogart, Bacall makes the first move and plants a kiss on Bogart. “What’d you do that for?” he asks. She replies, “Been wondering if I’d like it.” Maybe Bacall’s character, Marie ‘Slim’ Browning, was onto something with her “try before you buy” attitude.

Did you know that 59% of men and 66% of women say they’ve ended a potential relationship because of a bad kiss?

If you’re trying to decide whether or not someone is relationship material, a kiss can be a good way to find out. Lips are filled with sensitive nerve endings, so lip-to-lip contact triggers a love cocktail of hormones and neurotransmitters. The “spark” you feel with that special someone is actually the sensation of electric impulses bouncing between your lips, brain, tongue and skin. Each person has a distinct natural scent and when you kiss, you subconsciously exchange biological information that provides insight into long-term compatibility.

According to a study conducted by two experimental psychologists from Oxford University, Rafael Wlodarski and Robin Dunbar, kissing can be used as a tool to assess potential mates and then maintain those relationships. In terms of relationship happiness, the participants in committed relationships rated frequency of kissing as more important than sexual intercourse. They believe kissing enhances the affection for and attachment to their significant other.

Gone With the Wind

The long-awaited kiss between Rhett Butler and Scarlett O’Hara in Gone With the Wind is probably one of the most famous cinematic lip-locks of all time. Rhett’s smooth line, “You should be kissed, and often, by someone who knows how,” is probably just as famous as the kiss itself.

Did you know kissing is good for your health?

His flirting could be taken as wellness advice, since kissing can strengthen immune defense, decrease stress levels, and even burn calories! (Fun fact: You can burn 6.4 calories per minute during passionate kissing.) In a 2009 study at Arizona State University, a group of adults told to increase the amount of time spent kissing their partner showed a significant decrease in stress levels afterward, and some even showed lower cholesterol levels. If Scarlett had been kissed often, she may have been a lot healthier—and maybe less of a drama queen!

The Notebook

It’s hard to forget the rain-soaked make-out between Rachel McAdams and Ryan Gosling in “The Noteboook.” “It still isn’t over,” Gosling’s character says as he picks up and passionately kisses his former love. Though this takes place seven years after the relationship ended, the two are more smitten than ever. One kiss has the power to reconnect them after all those years apart.

Did you know you can be addicted to your partner’s kiss?

Research shows that kissing is a decisive litmus test for a relationship. Sebum, a chemical released in the glands in the mouth and on the body, is exchanged in saliva and plays an important role in bonding with a partner. According to Bubba Nicholson, a researcher at Georgia Tech, you can actually become “addicted” to your partner’s sebum. Humans have more sebaceous glands than we’ve previously bonded with. As unromantic as it sounds, the characters in “The Notebook” probably shared a mutual biological “addiction” to each other’s unique chemical combination. But most will agree that “it still isn’t over” is much more romantic than “I can’t live without your sebum.”

Do you have a favorite movie kiss that’s not on our list? Tell us… we’d love to hear from you!

Click here to see Rose’s tips for healthy and happy relationships