Here is a state-of-the-art review of our current knowledge of brown dwarfs and very low-mass stars. The hunt for, and study of, these elusive objects is currently one of the most dynamic areas of research in astronomy. This volume presents review articles from a team of international authorities who assess the spectacular progress in this field in the past few years. The contributed chapters review both the latest observations and theories, making this an essential reference to one of the most exciting fields in contemporary astronomy.