I present two recent observational results, which can provide <br /><br />
constraints on models of galaxy formation and evolution. First, I <br /><br />
report on photometric metal abundance estimates for individual <br /><br />
main-sequence stars in the Virgo Overdensity, which is believed to be <br /><br />
the remains of a merging dwarf galaxy in the Galactic halo. I discuss <br /><br />
the principles behind the technique that is based on a calibration of <br /><br />
the metallicity sensitivity of stellar isochrones in the Sloan Digital <br /><br />
Sky Survey (SDSS) passbands. Second, I report the detection of several <br /><br />
molecular gas-phase and ice absorption features in three <br /><br />
photometrically-selected young stellar object (YSO) candidates in the <br /><br />
central 280 pc of the Milky Way. Our spectra, obtained with the <br /><br />
Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, <br /><br />
demonstrate the youth of these objects, and provide the first <br /><br />
spectroscopic identification of massive YSOs in the Galactic Center.