This outstanding collection of surveys addresses graduateand predoctoral students. It reports on theoretical researchand observational data on active galactic nuclei: The enigmaof the nuclei of galaxies with their central "monster"driving the vast range of activity observed in quasars,radio galaxies, Seyferts, starburst galaxies and even ourown Galaxy are explored in this volume. Topics coveredinclude: the impact of recent measurements in the infraredand radio region on our knowledge of thenucleus of ourGalaxy; the spectra and classification of active galacticnuclei, the properties of their host galaxies, theircosmological distribution and evolution, the role of starsand thehydrodynamics of the interstellar medium in thenuclei; the description of the inner parsec of a standardactive galactic nucleus based on direct interpretation ofthe observations; the infrared activity of galaxies; thephysics of radio galaxies and their jets, emphasizing thephysics ofgas flow and high-energy particle interactions aswell as shock acceleration. These are all discussed inconsiderable depth and presented inself-contained chapterswith exhaustive reference lists of the scientificliterature.