How are diet and lifestyle linked to bacterial communities in the gut? How can growing knowledge about gut health be used to develop new therapies? Researchers are learning how the gut microbiome responds to the food we eat, influencing obesity, autoimmune disorders, cardiovascular disease, and even mental health. Trillions of bacteria inhabit the human gut, working in close and complex symbiosis with our cells. Novel analytic methods offer new insights about those biochemical interactions, and help us understand how they impact well-being. When it comes to a healthy body and mind, an increasing number of people are focusing on improving bacteria in the gut.