Abstract
Creatures on Earth have circadian system to live efficiently in light/dark cycle of 24-hour. After twilight, core body temperature and alertness start declining following beginning of melatonin secretion in human. These physiological functions help us sleep soundly. In the first half of this paper, core body temperature and melatonin known as indices reflecting circadian rhythmicity are explained regarding the relationship between its circadian variation and sleep. Later, some specific ways to support sound sleep by designing lighting environment and bedroom from the viewpoint of circadian physiology are introduced. (Japanese Journal of Physiological Psychology and Psychophysiology, 25 (1) : 73-87, 2007.)
