1. When you kiss someone for the first time, you get a spike in the neurotransmitter dopamine, making you crave more.
2. Dopamine can also make you lose your appetite and make it hard for you to sleep.
3. Two thirds of people tilt their head to the right when they kiss.
4. Kissing helps us work out if someone is a good match.
5. When you kiss someone your heart beats faster and more oxygen reaches your brain.
6. And it makes your pupils dilate.
7. Endorphins released during kissing bring on waves of euphoria.
8. The muscle you use to pucker your lips is called the "orbicularis oris".
And the shape you make with your mouth mirrors that of a breastfeeding baby, hinting at one possible way that kissing evolved.
9. Nachküssen is a German word that means "a kiss to make up for those that have not occurred".
10. Kissing triggers the release of oxytocin in your body.
11. More kissing in a relationship is related to how satisfied people say they are in that relationship.
12. Women tend to rate kissing as more important in relationships than men do.
13. The world record for the longest kiss stands at well over two days.
14. Your lips have a disproportionate number of nerve endings compared to other parts of your body.
15. When your lips touch someone else's 5 out of 12 of your cranial nerves are engaged.
16. Over time, kissing lowers your levels of stress hormone cortisol, making you feel all safe and secure.
17. Most people remember their first kiss more vividly than the first time they had sex.
Additional source: The Science of Kissing by Sheril Kirshenbaum.