String theory is radically changing our ideas about the nature of space, opening up the possibility that extra dimensions, rips in the fabric of space, and parallel universes actually exist. This NOVA program explores the idea of wormholes, reviews the development of string theory and M-theory, examines how M-theory calls for a universe with 11 space-time dimensions, and speculates that additional dimensions might help explain why gravity is much weaker than QT's other fundamental forces.