My main topic of research is the chemical evolution of the Universe, I would like to understand how the Universe evolved from a very simple chemical composition (H, He and traces of Li) to the current complex chemical composition. My main tool is spectroscopy, through spectra of astronomical objects (e.g stars, interstellar or intergalactic medium) one can derive their chemical composition and by observing objects of different ages one can reconstruct how the chemical composition evolved. After earning my PhD i began to work as astronomy researcher at the Astronomical Observatory of Trieste (Italy), from where I moved in 2005 to set-up the Marie Curie Excellence Team "Cosmological Impact of the First STars" at Observatoire de Paris (OP). I then remained in Paris, as director of the OP department Galaxies Etoiles, Physique et Instrumentation for nine years. Since 2010 I am Directeur de Recherche CNRS at GEPI-OP-PSL.