Deep sleep, also known as slow-wave sleep, is a crucial stage of the sleep cycle characterized by slow brain waves and reduced physiological activity. During this phase, the body undergoes important restorative processes, such as tissue growth and repair, immune system strengthening, and energy replenishment. It typically occurs in the first half of the night and is essential for overall health and well-being. This stage of sleep is vital for memory consolidation and learning, as it helps the brain process and store information from the day. Lack of deep sleep can lead to various issues, including fatigue, impaired cognitive function, and increased stress levels. Prioritizing good sleep hygiene can enhance the quality of deep sleep.