In eighth grade, I got home from school one day and told my mom that I had “friction” with a boy in my class. She laughed in my 13-year-old face and said, “You mean, ‘chemistry’?!” That is indeed what I meant. But to this day, I still don’t understand the chemical factors that go into feeling physically and emotionally pulled toward another person. What’s the science of attraction? And what does it mean to have chemistry anyway?

The science of why people get together isn’t a perfect one, notes Harvard University’s blog Science in the News. But there are chemical components to the sexual chemistry equation. And I’m not talking about iodine (I), livermorium (Lv), yttrium (Y), oxygen (O), and uranium (U). (Get it? “I love you?” I made a chemistry joke!) I’m talking about hormones.

In a simple graphic, created by Tito Adhikary, the categories of love, lust, and attraction are paired with the hormones that contribute to each. So sexy, right?

Learn the science of attraction with 3 equations that dictate sexual chemistry

Lust = Testosterone + Estrogen

The hypothalamus of your brain stimulates the production of both testosterone and estrogen—the sex hormones of the body that make you want to get it on with the person you desire. Whether your sex is male or female, your body possesses both of these chemicals.

Love = Dopamine + Norepinephrine – Serotonin

Our brains release dopamine as a reward when we do something pleasurable, like, I don’t know—sex. Norepinephrine is a result of attraction and can often lead to a lack of appetite and insomnia. (“I’m in love! I can’t eat! I can’t sleep!”) Finally, your serotonin levels decrease, affecting both your mood and hunger.

Attachment = Oxytocin + Vasopressin

How cute is this—oxytocin is known as the “cuddle hormone.” It’s released during sex, childbirth, and breastfeeding, and has the effect of bonding people together. Vasopressin causes similar I-just-want-to-squeeze-you reactions.

You might be thinking: Okay, easy! I just need to find a partner who kicks my lust, love, and attachment hormones into high gear. But I’m sorry to report that even perfectly matched couples find trouble in paradise. Too much dopamine and oxytocin, for example, clouds judgement and leads to overreliance on one another for support. Beyond the chemicals, keep it interesting by making your own rules.

Are you in love or are your hormones tricking you? Here’s how to tell. Plus, what to do if the sound of your partner chewing food makes you want to break up.