Introduction -- What is a galaxy?- Galaxies in general -- The difference between 'ordinary' and active galaxies -- The panoply of active galaxies: (Quasars, QSOs, Radio galaxies, BL Lacs, Blazars, LINERS, ULIRGS, Seyfert galaxies, Starburst galaxies, N galaxies, etc.) -- What they are and what they do? (The images of many active galaxies are beautiful and spectacular, and the inclusion of a significant number of colour photographs is essential to the book.) -- Active galaxies across the spectrum (Activities and behaviours at radio, infrared, ultra-violet, x-ray and gamma ray wavelengths) -- Explosions and jets -- Multiple jets and why there is sometimes only one jet -- Faster than light -- Superluminal motions and how they occur -- The central black holes -- Evidence for their existence -- Nature and properties of super-massive BHs -- Jets and accretion disks -- Energy sources -- How BHs produce the features of active galaxies?- How the BHs form?- Could the Milky Way become an Active galaxy?- What would happen to life on Earth?- What will happen when the Milky Way and the Andromeda galaxy collide in 3,000 million years?- Observing active galaxies using small telescopes -- Observing data (positions, magnitudes etc.) for the brighter active galaxies -- Bibliography / web site list.