What sleep wake cycle is ultimately controlled by the part of the brain called?

The sleep-wake cycle is ultimately controlled by the hypothalamus, specifically a group of cells within it known as the suprachiasmatic nucleus (SCN). This region regulates circadian rhythms by responding to light and dark signals, helping to synchronize the body's internal clock with the external environment. Additionally, the hypothalamus interacts with other brain regions and neurotransmitters to promote wakefulness or sleep.