Atomic jets and molecular out?ows from Young Stellar Objects (YSOs) are among the most spectacular of astrophysical phenomena. Approaching this topic, one gets immediately trapped by the breathtaking beauty of the op- calimagestakenfromEarthorSpacewithmoderntelescopes, onlytodiscover soonafterthatthephysicsthatregulatestheirpropertiesisevenmoreintri- ing. Out?ows are believed to play a fundamental role in the formationprocess of a new star and its planets, as they could be the principal agent for the removal of the excess angular momentum from the star-disk system. Their generation mechanism,...