On average properties of inhomogeneous cosmologies

The present talk summarizes the recently progressed state of a systematic re-evaluation of cosmological models that respect the presence of inhomogeneities. Emphasis is given to identifying the basic steps towards an effective (i.e. spatially averaged) description of structural evolution, also unfolding the various facets of a `smoothed--out' cosmology. We shall highlight some results obtained within Newtonian cosmology, discuss expansion laws in general relativity within a covariant fluid approach, and put forward some promising directions of future research.