The light we see is as important for our health as the food we eat, the water we drink, and the air we breathe. For most of human existence, our ancestors lived with the natural 24-hour light-dark cycle, spending each day in natural daylight and sleeping in the dark at night. But since the widespread introduction of electric light, more than 90 percent of our time is spent indoors, under unhealthful and human-unfriendly electric light, which disrupts our circadian clocks and greatly increases the risk of cancer, obesity, diabetes, heart disease, and hundreds of other diseases. The light doctor reveals extensive scientific evidence establishing the risks of blue-rich artificial light at night. Furthermore, it provides the practical information you need to counteract these risks at home, and in workplaces, schools, hospitals, and senior care facilities.