The trillions of microbes living on and inside the human body are an important part of who we are, from mediating all of our interactions with the environment to determining our cancer risk and influencing who we fall for. And scientists are only just beginning to decipher the species of bugs we share our lives with, and how they shape us. In the first of a Science Weekly three-part mini-series, Ian Sample speaks to colorectal surgeon and researcher, James Kinross, about the miraculous world of our gut microbiome, how modern life is impacting it, and what we can do to look after it. Help support our independent journalism at theguardian.com/sciencepod