Dynamo theory is the study of the generation and maintenance of magnetic fields by fluid motion. It is important in many areas of physics, ranging from stellar and galactic dynamics, through solar physics and geomagnetism to reactor physics. This volume is the only modern introduction to the subject, and is comprised of the lectures given by leading specialists for an intensive course held at the Newton Institute in Cambridge, U.K. as part of a NATO Advanced Study Institute. Topics covered include planetary and solar dynamos, fast dynamos, and the use of symmetry principles to derive evolution equations. Each chapter starts with background material and goes right up to the forefront of current research. Detailed bibliographies are provided. This book will be welcome reading for graduate students in planetary and solar physics, plasma physics, and astrophysics.