“Without bacteria, viruses, fungi, and other microorganisms, there wouldn’t be life on earth, and we wouldn’t be here,” says Lita Proctor. “Every kind of living thing is dependent on communities of microbes we call microbiomes, and that includes humans.” Proctor is director of the Human Microbiome Project, an eight-year research mission of the National Institutes of Health to explore the role of the microbiome in human health and disease. Here’s some of what we know so far...and what we still need to find out.