Sleep is fundamental for our body and mind. It is not only important how much we sleep, but also when we sleep, and under which environmental conditions. Naturally, our sleep-wake cycle would approximately follow the light-dark cycle – but nowadays, social and professional requirements often do not match with that. Most people do not get enough sleep or have irregular sleep wake schedules, which can have serious physiological and psychological consequences. Chrono Council informs and advices on the topics of sleep, biological rhythm and light.