The transient X-ray source GRS 1915+105 was discovered in August 1992 with the GRANAT/WATCH all-sky monitor (Castro-Tirado et al. 1994). Subsequent VLA observations from March through April 1994 led to the discovery of apparent superluminal motion in a pair of radio condensations moving away from the compact radio core (Mirabel & Rodriguez 1994). These jet-like features are interpreted as a bipolar outflow with bulk velocity ~ 0.9c. Although no optical counterpart has been observed, due to the heavy extinction in the Galactic plane, and therefore not enabling measurements of the mass of the compact object, the hard X-ray spectrum and high luminosity (~ 1039 erg s−1), extreme variability in the X-ray light curve and the relativistic jets make GRS 1915+105 a strong black hole candidate.