Human sleep is a natural state of rest characterized by reduced consciousness, sensory activity, and muscle relaxation. It plays a crucial role in physical and mental health, allowing the body to repair itself and the brain to process information. Sleep is divided into different stages, including REM (Rapid Eye Movement) and NREM (Non-Rapid Eye Movement), each serving unique functions. During sleep, the body undergoes various processes, such as hormone regulation and memory consolidation. Adults typically require 7 to 9 hours of sleep per night for optimal functioning. Factors like stress, diet, and lifestyle can significantly impact sleep quality and duration.