Origin of night dream has been an enigma through whole history of human race. Descriptions in the Bible have shown that the ancients regarded dream experiences as a consequence of the supernatural power outside. Since the early twentieth century, progresses of psychology have proposed that night dream comes from the unconscious mind inside. Finally in 1953, Aserinsky and Kleiteman discovered human REM sleep and demonstrated that dream reports were obtained most frequently when subjects were awakened from REM sleep. Thereafter, many scientists conducted studies on dream and REM sleep, and found a robust association between electrophysiologic phenomena and subjective experiences during REM sleep. Here we reviewed articles on psychophysiological aspects of dream and REM sleep. To document mnemonic functions of REM sleep was of our particular interest. The authors expect that studying dream and REM sleep gives clues to an understanding on the mind-body relationship.