The HH 212 interstellar laboratory: astrochemistry as a tool to reveal
  protostellar disks on Solar System scales around a rising Sun
  The investigation of star forming regions have enormously benefited from the
recent advent of the ALMA interferometer. More specifically, the unprecedented
combination of high-sensitivity and high-angular resolution provided by ALMA
allows one to shed light on the jet/disk systems associated with a Sun-like
mass protostar. Also astrochemistry enjoyed the possibility to analyze complex
spectra obtained using large bandwidths: several interstellar Complex Organic
Molecules (iCOMs; C-bearing species with at least 6 atoms) have been imaged
around protostars. This in turn boosted the study of the astrochemistry at work
during the earliest phases of star formation paving the way to the chemical
complexity in planetary systems where Life could emerge. There is mounting
evidence that the observations of iCOMs can be used as unique tool to shed
light, on Solar System scales (< 50 au), on the molecular content of
protostellar disk. The increase of iCOMs abundances occur only under very
selective physical conditions, such as those associated low-velocity shocks
found where the infalling envelope is impacting the rotating accretion disk.
The imaging of these regions with simpler molecules such as CO or CS is indeed
paradoxically hampered by their high abundances and consequently high line
opacities which do not allow the observers to disentangle all the emitting
components at these small scales. In this respect, we review the state-of-the
art of the ALMA analysis about the standard Sun-like star forming region in
Orion named HH 212. We show (i) how all the physical components involved in the
formation of a Sun-like star can be revealed only by observing different
molecular tracers, and (ii) how the observation of iCOMs emission, observed to
infer the chemical composition of star forming regions, can be used also as
unique tracer to image protostellar disks on Solar System scales.
