Love does a number on our bodies and brains, and there’s a reason the honeymoon phase of a relationship feels so amazing.

You probably already know that brain chemicals are the main culprits in the love experience, but did you know that the bacteria on your skin plays a role too? Here are some of the weird, wild things that go on inside your body when you fall for that special someone:

Your Brain In Love

Love is patient, kind, and intertwined with our biology. That feeling when your crush agrees to a date—let alone a first kiss—is a powerful one. However, what causes the desire to love other people? Our romantic entanglements are more chemically and biologically based than you might think.

Professor Xiaochu Zhang and his researchers conducted a study to find out exactly what love does to our brains. He began the study by dividing the 100 subjects into three groups: those intensely in love, people recently out of a relationship, and people who were single or had never experienced romance.

Researchers looked at the subjects’ brain activity with a resting state fMRI, which gave the scientists a complete map of the brain’s functional architecture. The researchers found that those who were in love had increased brain activity spanning several regions, including areas associated with reward, motivation, emotion, and social cognition.

The longer subjects said to have been in love; the more activity showed in their brains. However, those who were not in any romantic relationship showed less overall activity.

“This study provides first empirical evidence of love-related alterations in brain functional architecture,” the researchers wrote. “Furthermore, the results shed light on the underlying neural mechanisms of romantic love, and demonstrate the possibility of applying a resting-state fMRI approach for investigating romantic love.”

Now everyone’s going to want a resting-state fMRI scanner.

That Sweet, Sweet, Chemical Release

Unsurprisingly, the researchers found high levels of feel-good neurochemicals in the love-struck study subjects’ brains. Dopamine, serotonin, adrenaline, oxytocin, and norepinephrine all play starring roles in your love life. Dopamine and serotonin create feelings of elation and happiness, while adrenaline and norepinephrine are responsible for your sweaty palms and racing heart.

Oxytocin is a chemical that promotes bonding, intimacy, and trust between people. Hugging and cuddling cause a release of oxytocin, making you feel more connected with your partner.

Studies have found that the stress hormone cortisol is in high amounts in individuals who have recently fallen in love. While new love is full of cute dates and first kisses, it’s also a stressful experience.

Shared Spaces, Shared Bacteria

The typical next step for couples who are in long term relationships is to move in together. This process opens up a whole other level of biological connection. Not only do couples who live together share the same space—they share the same bacteria.

Researchers Ashley Ross, Andrew Doxey, and Josh Neufeld conducted a study to understand how the microbiomes on our skin adapt and change. They found that cohabitation had a strong association with a microbiome composition.

The study consisted of 340 skin samples from 17 sites all over the body from 10 couples. Researchers compared the samples with each person’s partner to find any similarities. The results showed that certain areas had more in common than others.

Because couples share a shower and walk barefoot on the same floors, feet have the most bacteria in common. How’s that for romance? Anyway, the next time you go in for a kiss from your significant other, just remember to thank all the chemicals and bacteria that keep your relationship going strong.