Kallyope, we believe that the gut is the gateway to our internal world. Containing millions of neurons, the gut informs our brains about our well-being, metabolism, and nutritional state. The gut-brain axis—the communication highway between our gut and our brain—offers an unprecedented opportunity to access and influence brain centers involved in fundamental human processes. An understanding of the biology mediated by the gut and gut-brain circuits will change the way we think about food, nutrition, and human physiology