We shall describe, without technicalities, the main ideas of an alternative approach for the last step in Perelman's proof of Thurston's Geometrization Conjecture. This is joint work with L. Bessieres, M. Boileau, S. Maillot and J. Porti. Using two covering arguments we reduce the problem to Thurston's proof of his conjecture for Haken manifolds. One of the arguments makes use of Gromov's simplicial volume.