Life on earth has evolved during the past several billion years under relatively bright days and dark night conditions. Virtually, all organisms on the planet display an internal representation of our rotating planet in the form of circadian rhythms. Among vertebrates, virtually every aspect of physiology and behavior, including metabolism, food intake, hormone secretion, body temperature regulation, mood, and sleep is mediated by these internal clocks. The widespread adoption of electric lights during the past century exposed animals, including humans, to significant light at night for the first time in their evolutionary history. Importantly, endogenous circadian clocks depend on light, especially short wavelength (i.e., blue) light, to entrain to the external daily solar environment. Thus, exposure to blue light at night can derange temporal adaptations. Indeed, disruption of natural light-dark cycles results in several physiological and behavioral changes with potentially serious implications for physiology, behavior, and fitness. In this talk, data from our lab will be reviewed on the role of dim light at night on metabolism and immune responses in rodents. The association among light at night, dysregulation of clock gene expression, and neuroinflammation will be presented.