Apart from comfortable bedding, what kind of environment promotes deep, refreshing sleep? Many studies have been carried out to determine the answer, and although much is still not understood, it is now thought that light plays a major role in determining the quality of one's slumber.
In general, sleep is said to become shallow if bedroom lighting is brighter than 30 lux (just bright enough to be able to read a book). It is also believed that the more morning sunlight your bedroom receives, the easier -- and earlier -- you'll wake up.
Early exposure to sunlight can also help ensure healthy sleep the following night. About 14 hours after our bodies are first exposed to sunlight, the brain secretes the hormone melatonin, which causes sleepiness.