  The Gaia mission is reviewed together with the expected contents of the final
catalogue. It is then argued that the ultimate goal of Galactic structure
studies with Gaia astrometry should be to build a dynamical model of our galaxy
which is capable of explaining the contents of the Gaia catalogue. This will be
possible only by comparing predicted catalogue data to Gaia's actual
measurements. To complement this approach the Gaia catalogue should be used to
recalibrate photometric distance and abundance indicators across the HR-diagram
in order to overcome the lack of precise parallax data at the faint end of the
astrometric survey. Using complementary photometric and spectroscopic data from
other surveys will be essential in this respect.
