The Human Microbiome Project and other microbiome projects worldwide have laid an important foundation for understanding the trillions of microbes that inhabits each of our bodies. However, opportunities for the public to get involved in such research has been limited. Now, American Gut gives you an opportunity to participate and to compare the microbes in your gut to those in the guts of thousands of other people in the US and elsewhere. American Gut is a project built on open-source, open-access principles. Our data are for the good of understanding and will be shared both with participants and with other scientists.