The IRAM interferometer has been used to map 3 high velocity outflows from Class 0 sources in SiO and CO rotational lines. The images show that such outflows are driven by highly collimated, dense, but optically invisible jets, through large travelling bow shocks. Precession is important in explaining some morphological and kinematic aspects. A significant part of the SiO emission is directly associated with the jet. Images of the molecular core surrounding L 1157 in CO isotopic lines show direct evidence for infall in a large, flattened disk.
For more evolved objects, “surveys” of mm emission from T Tauri stars provide evidence for circumstellar dust disks with relatively flat surface density distribution and typical radii 100 to 200 AU. Much larger gas disks (radii 800 to 1000 AU) have been detected and imaged in a few objects (2 singles and 2 binaries) through CO isotopomers, but in most sources 13CO is difficult to detect. The spectral line images provide unambiguous evidence for Keplerian rotation. In two cases (GG Tau and DM Tau), direct measurements of the gas mass (independently of the dust) has been made thanks to the detection of 7 molecular species. The molecules are found to be depleted by factors between 5 (for CO) to 100 (for H2CO). These results suggest that circumstellar disks consist in a small, dense, inner disk of outer radius ≃ 150AU (traced by the dust emission), surrounded by a much larger, less massive, outer disk (traced by the gas emission).