active galaxies, stellar-mass X-ray binaries have the advantage of varying on time scales accessible within a human life (sometimes even much shorter than a second). This has led to the ?rst detailed studies of the relation between accretion and ejection. It is even possible that, excluding their ¿soft¿ periods, the majority of the power in gal- tic sources lies in the jets and not in the accretion ?ows. This means that until a few years ago we were struggling with a physical problem, accretion onto compact objects, without considering one of the most important components of the system. Models that associate part of the high-energy emission and even the fast aperiodic variability to the jet itself are now being proposed and jets can no longer be ignored.