Current research on the origin and evolution of active galaxies is comprehensively surveyed in this collaborative volume. Both of the proposed types of central activity - active galactic nuclei and starbursts - are analysed with a particular emphasis on their relationship to the large-scale properties of the host galaxy. The crucial question is what triggers and fuels nuclear activity now and at earlier epochs? The topics covered here are gas flows near to massive black holes, the circumnuclear galactic regions, and the large-scale bars in disk galaxies. Aspects of nuclear bursts of star formation, and the relationship between central activity and the gas and stellar dynamics of the host galaxy are addressed as well. The contributors to this book for professionals and graduate students are world experts on galaxy evolution.