Physics of relativistic jets in blazars

Gamma-ray emission from blazars provides us with important diagnostics on the size and beaming factor of the emitting region as well as the energy densities of magnetic field, relativistic electrons and various radiation components. Through a simple analysis of multiwavelength observations, I argue that relativistic jets are kinetic power dominated and are composed mainly of electron-positron pairs and that particle acceleration in shock waves conforms very well with observations. I also discuss implications on the formation and bulk acceleration of relativistic jets.