  We know there is new physics at the electroweak scale, but we don't know what
it is. Right now, the top quark is our only window on to this physics. In
almost all models of electroweak symmetry breaking, top either couples strongly
to new particles or its properties are modified in some way. Top is being
studied in detail at the Fermilab Tevatron. Its production cross section has
been measured in a variety of channels; its mass has been determined to better
than 2%, and can be used to constrain the mass of the Higgs. Top quark decays
have been tested and non-standard production mechanisms searched for. Single
top production probes the electroweak properties of top, and has not yet been
observed; searches are now closing in on this process and it should be seen
soon. So far, all of the top quark's properties are consistent with the
Standard Model. However, the data still to come at the Tevatron will increase
the precision of all these measurements, and the enormous statistics available
at the LHC will open up new possibilities such as observation of spin
correlations and perhaps even CP violation in the top sector.
