The EROS project, a mostly French collaboration involving particle physicists and astrophysicists from DAPNIA, IN2P3 and INSU started LMC and SMC observations at the end of 1990, using photographic plates taken with the ESO Schmidt telescope at La Silla observatory (Chile). Nearly a year later, a dedicated wide field CCD camera mounted on a 40 cm telescope started operations at La Silla. In 1994, a more ambitious program was approved by the EROS team and the funding agencies in order to disentangle contributions from different Galactic components (disk, bar, halo) to the optical depths. The enlarged EROS collaboration, with Danish and Chilean participation started then the commissioning of EROS 2- MARLY dedicated wide field telescope and camera system.