Cosmic magnetic fields play a key role in the formation, structure and evolution of planets, stars and galaxies, and possibly the Universe as a whole. Magnetic fields of celestial bodies have been studied for a century, since the discovery of the first extraterrestrial magnetic field by George Ellery Hale in 1908, but their origin and evolution remain open questions for fundamental physics and astrophysics. IAU Symposium 259 presents the first interdisciplinary and yet comprehensive review of the role of magnetic fields on all scales that involved astronomers and physicists from across the community. It gives a balanced account of both theoretical and observational aspects of topics ranging from Earth’s habitability to the origin of the universe. This volume gives a forefront research account on the current state of the art.