Research into active galactic nuclei (AGN) - the compact, luminous hearts of many galaxies - is at the forefront of modern astrophysics. Understanding these objects requires extensive knowledge in many different areas: accretion disks, the physics of dust and ionized gas, astronomical spectroscopy, star formation, and the cosmological evolution of galaxies and black holes. This new text by Hagai Netzer, a renowned astronomer and leader in the field, provides a comprehensive introduction to the theory underpinning our study of AGN and the ways that we observe them. It emphasizes the basic physics underlying AGN, the different types of active galaxies and their various components, and the complex interplay between them and other astronomical objects. Recent developments regarding the evolutionary connections between active galaxies and star-forming galaxies are explained in detail. Both graduate students and researchers will benefit from Netzer's authoritative contributions to this exciting field of research.

IAU Symposium 356 summarises the most recent results in the field of active galaxies and active galactic nuclei (AGN). These are some of the most luminous sources in the Universe, also the most distant ones that we can observe, so they are very important for understanding the early Universe and its evolution through cosmic time. This volume gives an overview of the current status in the field of active galaxies including: AGN multiwavelength observations; different AGN types and their properties; AGN variability; active supermassive black holes and properties of galaxies in which they reside; triggering, feedback and shutting off AGN activity; relativistic jets and environments of active galaxies; and AGN evolution. IAU S356 was the third IAU symposium organised in Africa in the past 100 years since the IAU was established, and the first one organised in Ethiopia, highlighting current developments in astronomical research in Africa.