The human microbiome is the bacteria, viruses, and fungi that cover our skin, line our intestines, and flourish in our body cavities. Work on the human microbiome is new, but it is quickly becoming a leading area of biomedical research. What scientists are learning about humans and ourmicrobiomes could change medical practice by introducing new treatment modalities. This new knowledge redefines us as superorganisms comprised of the human body and the collection of microbes that inhabit it and reveals how much we are a part of our environment. The understanding that microbes arenot only beneficial but sometimes necessary for survival recasts our interaction with microbes from adversarial to neighborly. This volume explores some of the science that makes human microbiome research possible. It then considers ethical, legal, and social concerns raised by microbiome research. Chapters explore issues related to personal identity, property rights, and privacy. The authors reflect on how human microbiomeresearch challenges reigning views on public health and research ethics. They also address the need for thoughtful policies and procedures to guide the use of the biobanked human samples required for advancing this new domain of research. In the course of these explorations, they introduce examplesfrom the history of biomedical science and recent legal cases that shed light on the issues and inform the policy recommendations they offer at the end of each topic's discussion. This volume is the product of an NIH Human Microbiome Project grant. It represents three years of conversations focused on consensus formation by the twenty-seven members of the interdisciplinary Microbiome Working Group.