Since the invention of the light bulb, natural darkness is becoming increasingly invaded by artificial light. Once, light was considered unconditionally as an entire positive element: the more light the better. It increases safety and has a positive effect on our moods. But light also has a dark side as scientists have started to reveal. Millions of killed insects and migratory birds, psychosomatic disturbances of humans and breast cancer are only some of the effects light can cause.