Planet You: The mysterious world of the microbiome
There are trillions of them on -- and in -- our bodies. Microbes have existed on earth for more than three and a half billion years. Makes you wonder who's playing host to whom, and whether we humans are merely vessels for these tiny survivors. They influence everything from intestinal disorders to mental health conditions -- and we're only just beginning to understand their power over us. Contributor Stephen Humphrey journeys into the mysterious world of the microbiome.