We present the first results of a study of the expected properties of the first stellar generations in the Universe. In particular, we consider and discuss a series of properties that, on the basis of the emission from associated HII regions, permit one to discern { \it bona fide} primeval stellar generations from the ones formed after pollution from supernova explosions. The expected performance of NGST for the study and the characterization of primordial sources is also discussed.
Categories: astro-ph