Resumen
Great advance has been made recently in the understanding of the collimated outflow phenomenon frequently found in association with young stars, in particular in what refers to its large scale (tenths of pc or more) manifestations. These manifestations include the Herbig-Haro objects and the molecular bipolar outflows. Our understanding of the "engine" that power these outflows is, however, still limited. There is some consensus in the sense that the acceleration and collimation of these winds involved magnetohydrodynamic processes in an accretion disk, but observations with very high angular resolution are needed to test the models. At present, one of the best available techniques to study outflows with the required high angular resolution is the observation of thermal jets using radio interferometers. In this review, I discuss recent examples of results obtained with this technique.
