The uterus or womb symbolizes the feminine principle, the Mother Earth that gives birth to all things. It refers to what is not yet manifested, but also alludes to all potentialities. In many primitive religions, initiatory ceremonies were performed in caves that symbolized the return to the womb, so that the emergence from that place signified a rebirth. The alchemists established the following correspondences: the womb was a mine hidden in the earth, the mineral served as an embryo that the human being took the place of the midwife.