  We present results from an extensive spectroscopic survey in the 3-5 micron
wavelength region of low-mass young stellar objects using VLT-ISAAC. Medium
resolution spectra (R ~ 1000-10000) of young embedded stars in the mid-infrared
allow for detailed studies of ro-vibrational lines from molecular gas,
interstellar ices and Polycyclic Aromatic Hydrocarbons (PAHs). By taking
advantage of this wide range of molecular tracers available within a few
spectral settings, the survey has helped to constrain the chemical evolution of
cold molecular material in low-mass star forming regions as well as the physics
of disks surrounding protostars. In this contribution, we will review the
various spectral diagnostics of molecular material, which require ground-based
high resolution infrared spectroscopy. The importance of a high resolution
spectroscopic capability as will be offered by CRIRES is discussed in the
context of the physics and chemistry of low-mass star formation.
