The human eye is much more than the organ of vision. In addition to the machinery of the eye that allows us to see, the retina also houses photoresponsive molecules (photoreceptors) that mediate non-visual, light-driven signaling pathways. Our biological clock is regulated by the input of these light signals, including the circadian (24-hour) oscillation of our biochemistry, physiology, and behaviour. Many human functions rely on circadian rhythm and its accurate synchronization with the outside world by light (circadian phototransduction), including sleep, hormone regulation and brain function. Despite its central role in human health, however, virtually nothing is known about circadian phototransduction, including the light-driven events in a key photoreceptor called cryptochrome. Dr. Melanie O’Neill aims to uncover these events and to describe the mechanism of action of cryptochromes as circadian photoreceptors at the molecular and cellular level. Her research will provide a critical link between light input and biological response, and offer the basis for a description of circadian phototransduction that rivals our detailed description of vision. This research will enable an understanding and potential manipulation of biological timing that may transform our view of human health and our treatment of a host of human diseases including sleeping disorders, depression, and cancer.