studying physical, mental, and social changes in people as they age investigating the biological aging process itself including aging's causes, effects and mechanisms (biogerontology) investigating the social and psycho-social impacts of aging (sociogerontology) investigating the psychological effects on aging (psychogerontology) investigating the interface of biological aging with aging-related diseases (geroscience) investigating the effects of an ageing population on society (demography) exploring the relationship between the aging and their environment (environmental gerontology) applying this knowledge to policies and programs, including the macroscopic (for example, government planning) and microscopic (for example, running a nursing home) perspectives.