Which sleep stage is most strongly associated with vivid dreaming and rapid eye movements?

REM, or rapid eye movement sleep, is the sleep stage most strongly linked to vivid dreaming. It was first identified in the 1950s by Nathaniel Kleitman and Eugene Aserinsky, who noticed bursts of eye movements during sleep. REM sleep is also characterized by brain activity that is more similar to wakefulness than to deep sleep, along with muscle atonia, which helps prevent people from acting out dreams. Across a normal night, REM periods tend to become longer toward morning. While dreams can occur in other stages too, REM is the stage most famously associated with them.