Parsec-scale structure of quasars: dawn of the golden age?
  Half a century after their discovery, the study of quasars remains one of the
most fascinating intellectual challenges in astronomy. Quasars are laboratories
for everything from relativity to magnetohydrodynamics and are perhaps the best
available probes for cosmology. A tremendous amount has been learned about
quasars and yet many of the most fundamental questions about their physics
remain open. Parsec-scale observations have played an indispensable role in
building up our current understanding of quasars; virtually everything we know
about quasars depends on such observations. However, the finest hour for parsec
scale observations may be just beginning. This is partly due to the development
of highly reliable VLBI networks (which is continuing) but mostly due to the
unprecedented availability of multiepoch, simultaneous, broadband observations
that have long been the `holy grail' for quasar researchers.
