  A standard paradigm is now available for the recent evolution (z < 10) of
structure on galactic and larger scales. Most of the matter is assumed to be
dark and dissipationless and to cluster hierarchically from gaussian initial
conditions. Gas moves under the gravitational influence of this dark matter,
settling dissipatively at the centres of dark halos to form galaxies. The
evolution of the dark matter component has been studied extensively by N-body
simulations. The abundances, density profiles, shape and angular momentum
distributions and the formation histories of the dark halo population can all
be predicted reliably for any hierarchical cosmogony. The systematic variation
of these properties with halo mass can produce scaling relations in the galaxy
population. Simple hypotheses for how galaxies condense within dark halos lead
to characteristic luminosities, sizes, and spins which are close to those of
real spiral and elliptical galaxies. Furthermore, correlations similar to the
Tully-Fisher, Faber-Jackson and luminosity-metallicity relations arise quite
naturally. A quantitative explanation of the fundamental plane of elliptical
galaxies appears within reach.
