Work in clinical and laboratory settings has indicated that lack of bright light during the day can compromise mood, accelerate cancer growth, and impair cognition. Even sustained exposure to the equivalent of a child's night light has been shown to have an impact on everything from how well our brains function every day to how well our bodies recover from injury. Professor Randy J. Nelson brings together the most reliable research on the different ways exposure to light at night affects how our bodies function and, ultimately, our health. Each chapter explores the role of light and dark in our bodies' most important regulatory processes. In humans, virtually every aspect of our physiology and behavior is mediated by our internal biological clocks. One feature of modern life that may have negative consequences for our health is exposure to light levels that are not aligned with the 24-hour solar day. Circadian rhythms, the internal biological rhythms of our body's processes, require short wavelength (blue) light early during the day to optimize their temporal regulation. Experiencing light at night or insufficient light during the day can lead to a host of problems such as obesity, major depression, bipolar depressive disorder, seasonal affective disorder, sleep disorders, cancer, heart disease and more. Dark Matters sets out to shine a light on the health and well-being consequences of poor circadian hygiene and provide strategies to offset the negative health effects of disrupted circadian rhythms.