Through numerical N-body simulations of Lemaitre-Tolman-Bondi void models we
study the non-linear collapse of dark matter into halos. We extend the halo mass function
formalism to these models in a consistent way. This extension not only compares well with
the simulated data at all times and radii, but it also gives interesting hints about the
impact of the background shear on the growth of perturbations. Furthermore, the study of
the shapes and orientations of halos in these models shows specific features that could
be used to constrain them further.