This volume contains the lectures presented at a workshop at Ringberg Castle in 1986 on Interstellar Magnetic Fields on the occasion of the 60th birthdays of Rudolf Kippenhahn and Hermann Ulrich Schmidt. It covers a wide span of seemingly disparate topics ranging from comets, the sun, single and binary stars to active galactic nuclei. Although the astrophysical objects addressed are quite different, the physical processes involved are very much the same. The emphasis on the common physics underlying this wide variety of celestial phenomena makes this a unique book for researchers and students of astrophysics and astronomy.