Tufts/CfA/MIT Cosmology Seminar, at CfA: Andrew Liddle, University of Sussex Title: Observational Probes of the Very Early Universe Abstract: Cosmological inflation provides a theory for the initial conditions for structure formation in the universe. In order to capitalise on the rapidly improving observational situation, it is necessary to ensure accurate predictions from inflation. In particular, inflation produces gravitational waves as well as density perturbations and they may provide a distinctive probe of the inflationary paradigm. Finally, a survey is made of the present observational status of inflation-based structure formation models, covering both microwave background anisotropies and large scale structure observations such as galaxy clustering and object abundances.