In 2001 it was discovered that it is only the blue component in ordinary white light that causes melatonin suppression. Melatonin is the hormone that promotes sleep and is a powerful cancer fighter. This book traces the story of how research with animals and humans has demonstrated the health benefits of long periods of darkness that maximize melatonin. By blocking just the blue light a condition of "virtual darkness" allows enjoyment of normal evening activities while maximizing melatonin flow. The benefits go far beyond better sleep and reducing cancer risk. They include helping to avoid postpartum depression, improving symptoms of ADHD, and helping to stabilize mood in patients with bipolar disorder.