The NIH is divided into two parts: the "Extramural" parts of NIH are responsible for the funding of biomedical research outside of NIH, while the "Intramural" parts of NIH conduct research. Intramural research is primarily conducted at the main campus in Bethesda, Maryland and the surrounding communities. The National Institute of Aging and the National Institute on Drug Abuse are located in Baltimore, Maryland, and the National Institute of Environmental Health Sciences is in the Research Triangle, North Carolina. The National Institute of Allergy and Infectious Diseases, NIAID, maintains Rocky Mountain Labs in Hamilton, Montana, with an emphasis on virology.