  In the framework of brane-world models lowering the Planck scale to the TeV
range, it has recently been pointed out that small black holes could be formed
at particle colliders or by neutrinos interactions in the atmosphere. This
article aims at reviewing other places and epochs where microscopic black holes
could be formed : the interstellar medium and the early Universe. The related
decay channels and the propagation of the emitted particles are studied to
conclude that, in spite of the large creation rate for such black holes, the
amount of produced particles do not conflict with experimental data. This
shows, from the astronomical viewpoint, that models with large extra dimensions
making the gravity scale much lower are compatible with observations.
