Light affects human health and well-being by affecting our ability to see the world, perceive distances and spatial relationships as well as modulating our circadian system. The circadian system which maintains the body's 24-hour cycle is entrained by the light and dark cycles of day and night as well as an internal oscillator located in the brain and a hormone melatonin. The circadian system regulates many of the bodies activities including sleep. A majority of older adults in long term care facilities suffer from sleep problems.