The contributions to the 151st IAU Colloquium cover different fields of recent research, observational as well as theoretical, on solar and stellar flares ranging from radio up to gamma-ray wavelengths. A special chapter is devoted to all-sky monitoring and, finally, the excerpts of a round-table discussion present the reader with an interesting outlook on future developments. This book is therefore a unique source for those who want to get a complete picture of this fascinating part of modern astrophysics.