More than three decades have passed since our present picture of extragalactic radio sources began to unfold. The latter half of that time has witnessed the ‘mapping’ or ‘imaging’ of jet-like structures in many of these sources, and the realisation that apparently similar phenomena are associated with many Galactic objects. Numerous books have discussed instrumentation and radiation processes; overviewed the physics underlying both extragalactic and Galactic sources, and their intervening media; and attempted to present a coherent picture of the AGN phenomenon. And yet, although some excellent reviews have appeared, no book has addressed the subject of astrophysical jets in a detailed and comprehensive manner. This volume is an attempt to fill that gap.

What makes such a volume particularly timely, is that we are now digesting the first generation of high-resolution observations of extragalactic jets (MERLIN, VLA and VLBI data), the first generation of numerical simulations (mostly two-dimensional and nonmagnetic), and the first generation of theoretical studies, which have given us a quantitative framework for estimating physical properties and energetics, and for discussing jet formation, propagation, and stability. Now is a time to take stock, as we await the first results of the VLB Array, satellite VLBI, three-dimensional and MHD simulations, and more refined theoretical studies. It also seems timely to compare and contrast the bodies of research on extragalactic and Galactic objects.

In order to achieve a detailed, comprehensive and critical text, it has been necessary to adopt a multi-author approach.