The National Institutes of Health (NIH), through its own research and the distribution of grants, seeks to understand disease inside and out. Part of the US Department of Health and Human Services, NIH is the government's main medical research entity. It comprises 27 institutes and centers covering every medical discipline, from general medical sciences to alternative therapies. The organization has some 6,000 scientists of its own and gives out thousands of grants to researchers at more than 2,500 universities, hospitals, and research labs in all 50 states. Among its vast array of projects, NIH has supported efforts to develop an AIDS vaccine, map human genetic variation, and study avian flu.