AIM- Astrophysique Interactions Multi-échelles

I present an overview of past, present and future research on microquasars and jets, showing that microquasars, i.e. galactic jet sources, are among the best laboratories for high energy phenomena. After remindind the analogy with quasars, I focus on one of the best microquasar representatives, probably the archetype, namely GRS 1915+105, and present accretion and ejection phenomena, showing that only a multi-wavelength approach allows a better understanding of phenomena occuring in these sources. Thereafter, I review jets at different scales: compact jets, large-scale jets, and the interactions between ejections and the surrounding medium. I finish by speaking about microblazars and ultraluminous X-ray sources. 1 Prelude to microquasars In 1979 was discovered the microquasar prototype: SS 433, a high-energy source exhibiting precessing jets at frame velocity 0.26c, with emission lines observed in the optical, showing that the jet content was baryonic (Margon, 1984). SS 433 is surrounded by a supernova remnant: W50, and there are clear signs of interaction between SS 433 jets and W50 nebula (see e.g. Dubner et al. 1998). The question which arose was then: how can a galactic object eject matter at such relativistic velocities (Γ=1.04)? This object exhibited such unusual properties, that it was probably impossible to foresee that, two decades later, jet sources would become quite common. SS 433 had everything of a microquasar, apart from the name. 2 Youth of microquasars: analogy with quasars In 1990, the SIGMA telescope, orbiting on board Granat, was launched. It was designed to observe galactic black hole candidates, because its observing energy band corresponded to the