Quasar lensing
  I review the observations of gravitationally lensed quasars. These systems
are important because they allow us to probe the properties of the lensing
galaxies at various scales, and they also allow insights into the structures of
the quasars themselves. Samples of quasar lenses also have the potential to act
as cosmographic probes. These areas are described, together with observational
and scientific prospects for the future.
