  The currently available cosmological data yield, as a most striking result,
that the expansion rate of the universe seems to be increasing at late times,
contrary to the standard (zero cosmological constant) FLRW prediction. The
usual explanation for this discrepancy is that a new component of the energy
density of the universe, known as dark energy, dominates this recent evolution.
Since the existence of such a new component would have a revolutionary impact
on our understanding of the fundamental laws of physics, we think important to
check other interpretations. We have therefore shown that the SNIa observations
could be reproduced by the effect of inhomogeneities. This idea has been
further developed by different teams, and enlarged to other cosmological data.
We will give here a review of the results of these works and the prospects for
future developments.
