Mother of Pearl, or nacre is the iridescent substance that is a secretion of the mantle tissue of some fresh and salt-water mollusks. The chief sources are the pearl oyster, found primarily in Asia and freshwater pearl mussels, which live in many rivers of the United States, Europe, and Asia; and the abalone of California, Japan, and other Pacific regions.

This iridescent inner layer has been used for centuries in making jewelry as well as furniture, art and architecture.

Ho Hsien-Ku (the Immortal Maiden) - One of the Eight Immortals of the Taoist tradition - dreamed that she could become immortal by eating a powder made of mother of pearl. She appears only to men of great virtue.