What are the stages of sleep identified in sleep research?

The classification of sleep stages into non-rapid eye movement (NREM) and rapid eye movement (REM) sleep is widely accepted in sleep research. During NREM sleep, which includes stages of light and deep sleep, the body undergoes various restorative processes, such as tissue growth and repair, lowering of heart rate, and regulation of hormones. In contrast, REM sleep is characterized by increased brain activity, vivid dreams, and temporary muscle paralysis, which plays a crucial role in cognitive functions, including memory consolidation and emotional regulation. This classification provides a comprehensive framework for understanding the cycles of sleep that individuals experience throughout the night, as well as the distinct physiological and psychological changes that occur within these stages.