Our epithelium is a small lining of our guts that contains a universe of different microbes, food particles, and other molecules, including a hormone that drives our emotions as well as our need for sleep and bowel movements. Known as serotonin, it is a neurotransmitter that is tied to our central nervous systems, a relationship that was the subject of recent study. This research found that adrenaline promotes action by these cells, indicating a relationship between our brains and our guts, although the nature of this interaction has not been fully uncovered. Additional studies are ongoing to learn more about how common GI conditions are affected by our gut-brain connection.