Modern Lightening affects the human Circadian System

Sun light has controlled the human life over most part of our existence. As consequence all body functions show a strong circadian rhythm. We sleep at night when our body temperature is low and we are awake during the day when body temperature is high. This all began to change with the invention of the artificial light. Our daily life transformed to a 24 hour 7 days per week operation. Particular with the new powerful modern light sources such as LED and OLED's there are new possibilities and new risks. We give a short overview when and why during the 24 hour day artificial light with high portion of the blue spectra is beneficial for us and when it disturbs our well-being.