The astral plane, also called the astral realm, or the astral world, or the soul realm, or the spirit realm, is a plane of existence postulated by classical, medieval, oriental, esoteric, and New Age philosophies and mystery religions. It is the world of the celestial spheres, crossed by the soul in its astral body on the way to being born and after death, and is generally believed to be populated by angels, spirits, or other immaterial beings. In the late 19th and early 20th century, the term was popularised by Theosophy and neo-Rosicrucianism.