This document discusses dreams and sleep. It begins by defining dreams as sensations, images, and hallucinations created by the brain during sleep. Sleep is necessary for tissue conservation, energy recovery, and possibly delaying aging. The stages of sleep include light sleep, deeper sleep stages 3 and 4 characterized by delta waves, and REM sleep when dreams occur and eyes move rapidly. Lucid dreams occur in REM sleep when one is aware they are dreaming and can control the dream. REM sleep behavior disorder involves acting out dreams physically and is associated with neurological conditions. It can be treated with medications.