We think of ourselves as wholly distinct organisms – separate from the environment around us, and independent of other organisms. But zoom in closer, and you’ll see that the truth is far more complicated. All plants and animals maintain vital symbiotic relationships with an unfathomable quantity and diversity of microorganisms. And we are no exception. This encompasses the microbes on us, and within us. The best known example of this phenomenon is the gut microbiome , or the collection of bacteria and other microbes living inside the gastrointestinal tract. The number of microorganisms inhabiting the gut has been estimated to be as high as 10 14 – that equates to around 10 times more bacterial cells than human cells! On this basis, it has been argued that we collectively are, in fact, superorganisms . Given their staggering numerical superiority, it shouldn’t be surprising to learn that the amount and types of bugs you carry in your gut can make a big difference in how you