His research is focussed mainly on the birth and early stages of stars, and he also studies Galactic X-ray sources. Among his contributions, the discovery of bipolar outflows from young stars, the elucidation of the driving mechanism of Herbig-Haro objects, and the detection of protoplanetary disks around young stars, are some of the highlights. This work provides the observational evidence needed to support the idea that young stars are formed surrounded by protoplanetary disks of gas and dust, from which planets will condense, just as must have occurred in our Solar System.