Stellar population astrophysics is facing a golden era, thanks to Gaia, VVV, PTF, OGLE, LSST etc. and related multi-object high-resolution spectroscopic surveys as Gaia-ESO, GALAH, APOGEE, WEAVE, MOONS-GAL and 4MOST, that are setting the observational framework for an exhaustive description of the Milky Way structure. Optical and NIR high resolution spectroscopy is crucial to provide the complementary, detailed chemical tagging of selected stellar populations.

Taking advantage of the unique very high resolution spectroscopic capability of the TNG, with the HARPS-N and GIANO-B spectrographs covering a large fraction of the optical and near-IR range out to the K band , we proposed a Large Program titled ''SPA - Stellar Population Astrophysics: the detailed, age-resolved chemistry of the Milky Way disk'' (Program ID A37TAC13, PI: L. Origlia) and observing time has been granted starting from June 2018.

The SPA Large Programme aims at obtaining high quality spectra of more than 500 stars in the Milky Way thin disk and associated star clusters at different Galactocentric distances, including the poorly explored inner disk. We are observing luminous giant and supergiant stars in young star clusters and associations as well as luminous Cepheid and Mira variables across the entire thin disk and Main Sequence and other evolved stars of open clusters in the Solar neighbourhood.

These spectra will allow us to measure the full set of iron-peak, CNO, alpha, light and neutron-capture elements and to provide a detailed mapping of possible gradients, cosmic spreads and other inhomogeneities of individual abundances and abundance ratios. We also expect to answer a number of open questions regarding disk formation, evolution and chemical enrichment, as well as to perform critical tests of stellar evolution and nucleosynthesis, thus maximising the scientific return and the overall legacy value for astrophysics.