The National Institutes of Health (NIH) is a part of the U.S. Department of Health and Human Services and is the primary agency for conducting and supporting medical research in the United States. Established in 1887, it aims to improve public health by advancing knowledge in various fields of medicine and biology. NIH consists of 27 institutes and centers, each focusing on specific areas of health, such as cancer, heart disease, and mental health. The organization funds research projects, provides training for researchers, and disseminates health information to the public, contributing significantly to medical advancements and public health policies.