Abstract
It is observed that from very early stages in their evolution, young stars produce high velocity, collimated outflows. These outflows are seen optically as Herbig-Haro (HH) objects and as molecular outflows at radio wavelengths. This paper discusses models which simultaneously attempt to explain the observed morphological and spectral characteristics of both HH objects and molecular outflows. Models of the lateral jet beam/environment interaction, models of the effects of a time-variability of the source, and models of the interaction of the head of a jet with the surrounding environment are discussed.
