Jet physics with GLAST

The discovery of strong high energy gamma-ray emission from a number of active galaxies with the EGRET instrument provided us with wealth of data on those enigmatic objects. We currently believe that the entire broad-band emission from the fraction of AGN detected by EGRET - known as blazars - arises in a jet moving at relativistic speed aligned closely to the line of sight. This presentation will give an overview of the observational properties and models for radiation processes for blazars. It will also highlight the next instrument, Gamma-ray Large Area Space Telescope (GLAST), to be launched in 2005, with the emphasis on the new insights into the nature of blazars that GLAST is likely to reveal.