Morpheus is a god associated with sleep and dreams. In Ovid's Metamorphoses he is the son of Somnus and appears in dreams in human form. From the Middle Ages, the name began to stand more generally for the god of dreams, or of sleep.

A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, although the dreamer may perceive the dream as being much longer than this.