  Molecular jets are seen coming from the youngest protostars in the early
phase of low-mass star formation. They are detected in CO, SiO, and SO at
(sub)millimeter wavelengths down to the innermost regions, where their
associated protostars and accretion disks are deeply embedded and where they
are launched and collimated. They are not only the fossil records of accretion
history of the protostars but also are expected to play an important role in
facilitating the accretion process. Studying their physical properties (e.g.,
mass-loss rate, velocity, rotation, radius, wiggle, molecular content, shock
formation, periodical variation, magnetic field, etc) allows us to probe not
only the jet launching and collimation, but also the disk accretion and
evolution, and potentially binary formation and planetary formation in the
disks. Here I review recent exciting results obtained with high-spatial and
high-velocity resolution observations of molecular jets in comparison to those
obtained in the optical jets in the later phase of star formation. Future
observations of molecular jets with a large sample at high spatial and velocity
resolution with ALMA are expected to lead to a breakthrough in our
understanding of jets from young stars.
