What chemical reaction makes us dream when we sleep at night?
We spend more than two hours dreaming each night. Scientists did not know much about how or why we dream until 1953 when researchers first described rapid eye movement (REM) and non rapid eye movement (NREM) as two basic forms of sleep. Most dreaming occurs during REM sleep as the person's eyes move back and forth rapidly. However, there is no muscle activity during REM sleep. Muscles are inactive and prevent us from acting out our dreams. Infants spend about 50% of their sleep time in REM sleep while adults spend about 20% of their sleep time in REM. Elderly people spend less than 15% of their sleep time in REM sleep. The main reason why we dream is still unknown.