There are about a hundred trillion microbes living inside your gut -- protecting you from infection, aiding digestion and regulating your immune system. As our bodies have adapted to life in modern society, we've started to lose some of our normal microbes; at the same time, diseases linked to a loss of diversity in microbiome are skyrocketing in developed nations. Computational microbiologist Dan Knights shares some intriguing discoveries about the differences in the microbiomes of people in developing countries compared to the US, and how they might affect our health. Learn more about the world of microbes living inside you -- and the work being done to create tools to restore and replenish them.