  Since this is a meeting on inflation the title of this talk should probably
have been ``The cosmos as a lab for inflation''. I will illustrate how, by
combining WMAP observations of the cosmic microwave background (CMB) with
smaller scales CMB experiments and large-scale structure surveys, it is
possible to constrain inflationary models. WMAP data in combination with these
external data sets, offers a window to the very early universe and the physics
of inflation: enables us to confirm the basic tenets of the inflationary
paradigm and begin to quantitatively test inflationary models. Understanding
the complex physics and complicated systematics of the low redshift
observations is crucial to make progress in this direction.
