The U.S. National Institutes of Health (NIH) is a part of the U.S. Department of Health and Human Services. It is the nation's medical research agency, responsible for conducting and supporting medical research to improve public health. The NIH funds a wide range of studies, from basic science to clinical trials, and works to advance knowledge in various health-related fields. Established in 1887, the NIH consists of 27 institutes and centers, each focusing on specific areas of health and disease. It plays a crucial role in understanding diseases, developing treatments, and promoting health through research and education.