  Highly collimated supersonic jets are observed to emerge from a wide variety
of astrophysical objects, ranging from Active Nuclei of Galaxies (AGN's) to
Young Stellar Objects (YSOs) within our own Galaxy. Despite their different
physical scales (in size, velocity, and amount of energy transported), they
have strong morphological similarities. Thanks to the proximity and relatively
small timescales, which permit direct observations of evolutionary changes, YSO
jets are, perhaps, the best laboratories for cosmic jet investigation. In this
lecture, the formation, structure, and evolution of the YSO jets are reviewed
with the help of observational information, MHD and purely hydrodynamical
modeling, and numerical simulations. Possible applications of the models to AGN
jets are also addressed.
