Our bodies carry around trillions of microbes -- bacteria, viruses, and other living things so tiny that we need a powerful microscope to see them. These microbes live in groups in many places on and inside our bodies, such as the skin, the mouth, nose, gut and (in women) vagina. While we still don’t know how they do it, many of these microbes help to keep us healthy, while others contribute to disease. Similarly, changes in our health can affect our microbes. So can things like where we live or work, our age, ancestry, health status, and diet—and probably many other things that we don’t know about yet.
People and microbes both have DNA, the material that contains genetic instructions that how the micros act in our bodies, how they live with each other and how we react to them. All of the different kinds of microbes that live on and inside us, taken together, are called the “human microbiome.” The purpose of the HMP (Human Microbiome Project) is to learn about the human microbiome by studying the microbes’ DNA, other chemicals that the microbes produce, human DNA, and how microbes interact with each other and with their human host to contribute to health and disease.