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\section{Introduction}   In many areas of astrophysics compact central objects accrete mass and angular momentum from a disk and at the same time they eject a highly collimated jet. This is seen for central objects as massive as AGN or as light as (proto) brown dwarfs. Jets from AGN or accreting neutron stars reach relativistic energies velocities  while the velocities are significantly lower material  in jets from  young stellar objects (YSOs). (YSOs) is significantly slower.  A large number of jets is observed in nearby star forming regions, where the jet composition and structure can be studied in great detail \citep[see the review by][]{2014arXiv1402.3553F}.  Jet launching starts in the early stages of star formation and continues until the accretion from the circumstellar disk cedes. Jets from very young stars are the most powerful and can sometimes be traced to a parsec from the source. In these systems, the central engine is still deeply embedded in a dense envelope of gas and dust and thus cannot be observed directly. As YSOs evolve, the envelope becomes thinner. Actively accreting low-mass stars in this stage are called classical T Tauri stars \citep[for a review see][]{2013AN....334...67G}. Their jets often only reach a few hundred AU (and are thus sometimes called ``microjets'' in comparison to the outflows from younger objects).  It seems reasonable to suspect that the same physics governs the launching from any type of young star and that the same processes occur close to the launch site, but observationally the inner few tens of AU are only accessible in CTTS, where we can study the initial properties before a jet interacts with the ambient medium.