The bacteria that inhabit our bodies have garnered much attention in recent months. In fact, the trillions of cells that make up a single person are outnumbered ten to one by bacteria! Long the recipients of negative attention for making people sick, these bacterial communities are increasingly credited for benefiting digestion, immunity, and beyond. Researchers are applying advances in sequencing technologies to categorize the diversity of bacteria that colonize a single person, termed the microbiome. The microbiome is now considered to be an important environmental factor that influences people’s susceptibility to disease, raising new questions about the long-term impact of antibiotics on human health.