Perseus is an outstanding case in which to study the physics of relativistic plasma and thermal gas, and the interplay between galactic nuclei and galaxy clusters. Ground and space observatories have recently provided some ground-breaking insights into the Perseus system, from a detailed image of a jet launched in the vicinity of a supermassive black hole, through VLBI, to an unexpected degree of turbulence in the cluster core, constrained by high energy resolution in x-rays. While preparing for the next generation observatories that will allow readers to address these questions in other systems, this volume provides some first steps in exploring topics relating to particle acceleration, energy transport between large and small scales and the role of magnetic fields in the launch of relativistic jets. Chapters deal with the latest results covering theory, observations, and numerical simulations, spanning a wide range in physical scales and energy ranges.