Caffeine Free: Blue Light Makes People Alert at Night

There's much more than meets the eye to how we perceive light, researchers have learned in recent years. The latest revelation: blue light helps fend off drowsiness in the middle of the night.

A small study of 16 volunteers found that exposure to short-wavelength light, or blue light, perked them up immediately.

full story at:
http://www.livescience.com/humanbiology/060201_blue_light.html