726. There’s a reason love is so complicated and indescribable — it’s actually three feelings in one. According to a team of scientists led by famous biological anthropologist Helen Fisher, romantic love can actually be broken down into three sensations: lust, attraction and attachment. And each feeling is characterized by its own set of hormones stemming from the brain.

727. When someone is in the attraction phase of love, high levels of dopamine and norepinephrine are released. Dopamine is known as one of the happiness hormones, and these chemicals can make people feel giddy and even euphoric. This reaction can also lead to decreased appetite and insomnia, which means you can actually be so “in love” that you can’t eat or sleep well.

728. If you’ve ever heard someone say they’re lovesick, they may have been onto something. Though it hasn’t been proven that love makes you physically sick, it does raise levels of cortisol, according to Richard Schwartz, associate professor of psychiatry at Harvard Medical School. Cortisol is a stress hormone that has been shown to suppress immune function, making you more likely to get sick.

729. When you fall in love, your brain releases a hormone called phenylethylamine, which is known as the “love drug.” The hormone is what’s responsible for making partners feel madly in love with each other. Phenylethylamine is also found in chocolate, which may explain why you can't stop after one piece.

730. Many scientists have gone back and forth on whether it’s the brain that falls in love or the heart. Based on her work, Syracuse University professor Stephanie Ortigue believes it is ultimately the brain, though the heart is related. “Activation in some parts of the brain can generate stimulations to the heart, butterflies in the stomach,” Ortigue wrote in the Journal of Sexual Medicine. “Some symptoms we sometimes feel as a manifestation of the heart may sometimes be coming from the brain."