AbstractThe Gaia mission will obtain accurate positions, parallaxes and proper motions for 10⁹ object all over the sky. In addition, it will collect low resolution spectroscopy in the optical range for ~10⁹ objects, stars, galaxies, and QSOs. Parameters of those objects are expected to be part of the final Catalog. Complete and up-to-date libraries of synthetic stellar spectra are needed to train the algorithms to classify this huge amount of data. Here we focus on the use of the synthetic libraries of spectra calculated by the Gaia community to derive grids of Single Stellar Populations as building blocks of population synthesis models.