I will review the astrophysical manifestations of black holes in the universe, namely, Active Galactic Nuclei, black holes in stellar binary systems, and Gamma-Ray-Bursts. Then, I will show that the discovery microquasars - stellar-mass black holes in our Galaxy that mimic, in smaller scale, the phenomena seen in quasars - opened the way for the understanding of the physics in the environment of black holes, in particular, the connection between the accretion of matter and the origin of the relativistic jets seen elsewhere in the universe.