I will review the three astrophysical manifestations of black holes: AGN/quasars, microquasars, and gamma-ray bursts of long duration. Then, I shall discuss the physical analogies among black holes of all mass scales, the observed coupling between accretion instabilities and relativistic ejections, and the open questions in this area of research, in particular, the role microquasars may have play in the re-ionization of the early universe.
Service d’Astrophysique