Far beneath our skin exists an unfathomable, ancient universe - an internal ecosystem that is critical to our health. Dr Martin Blaser invites us into the wilds of the human 'microbiome', unfurling its inner workings and evolution. For thousands of years, bacteria and human cells have co-existed in a relationship that has ensured the health and equilibrium of our body. But now, much like the natural world outside of us, our internal environment is being irrevocably destroyed. The culprit: some of our most revered medical advances - antibiotics - which appear to be linked to the epidemics of asthma, eczema, obesity, certain forms of cancer, and other diseases plaguing modern society.