This book presents many types of tidal phenomena. The contributions evolved from a seminar in Oberwolfach, Black Forest, where German experts on tidal research met in October 1994 to present their views and experience to interested graduate students and scientists in an informal way. The seminar focused on earth tides, tides of the atmosphere and the oceans, including solar-induced variations of the magnetic field and climate, and tidal phenomena in the planetary system and universe. This book has an introductory character, but some contributions describe the state of the art in tidal research.