“Guts for Brains!” It sounds like an insult, but it might be a compliment. As least it’s kind of true. That’s right. You have a brain in your intestines. The network of neurons lining your gut is often called “the second brain.” (If you want to get really technical about it, it’s called the enteric nervous system.) Your second brain won’t help much if you get stumped by your next maths exam, but it is responsible for that butterflies in the stomach feeling you might have when you realize you didn’t study enough. Your second brain does a lot of the work of digesting food, but also plays a big role in regulating emotions—as anyone who gets stomaches in response to bad news can tell you.