  In this paper we propose a model for the formation of the cosmological voids.
We show that cosmological voids can form directly after the collapse of
extremely large wavelength perturbations into low-density black holes or
cosmological black holes (CBH). Consequently the voids are formed by the
comoving expansion of the matter that surrounds the collapsed perturbation. It
follows that the universe evolves, in first approximation, according to the
Einstein-Straus cosmological model. We discuss finally the possibility to
detect the presence of these black holes through their weak and strong lensing
effects and their influence on the cosmic background radiation.
