Millimetre VLBI monitoring of AGN with sub-milliarcsecond resolution

Global millimetre VLBI allows detailed studies of the most central jet regions of AGN with unprecedent spatial resolution of a few 100-1000 Schwartzschild radii to be made. Study of these regions will help to answer the question how the highly relativistic AGN jets are launched and collimated. Since the early 1990s, bright mm-sources have been observed with global 3 mm VLBI. Here we present new images from an ongoing systematic analysis of the available observations. In particular, we focus on the structure and structural evolution of the best observed AGN jets, taking 3C 454.3 as a characteristic example. This core-dominated and highly variable quasar shows a complex morphology with individual jet components accelerating superluminally towards the outer structure. We briefly discuss the X-ray properties of 3C 454.3 and present its radio- to X-ray large-scale brightness distribution.