The Suprachiasmatic Nucleus (SCN) is a small group of nerve cells located in the hypothalamus of the brain. It plays a crucial role in regulating the body's internal clock, known as the circadian rhythm, which influences sleep-wake cycles, hormone release, and other physiological processes. The SCN receives information about light from the eyes, helping to synchronize the body's functions with the day-night cycle. The SCN is often referred to as the master clock because it coordinates the timing of various biological rhythms throughout the body. It communicates with other brain regions and organs to ensure that processes like metabolism and sleep occur at optimal times. Disruptions to the SCN can lead to sleep disorders and other health issues.