The formation of the first stars brought the infant Universe out of the dark ages and changed its chemical composition by producing the first heavy elements, which were dispersed into the surrounding gas via energetic supernova explosions. Metals, dust, and photons strongly affected the cooling properties of the gas, and hence the subsequent formation of stars and galaxies. In the Local Group, spectroscopic studies of individual stars provide us with the unique opportunity to reveal the chemical enrichment of the interstellar medium when the Universe was less than 1 Gyr old. In this talk, I will review the most recent findings for the chemical evolution of the Local Group, from both theoretical and observational perspectives. I will present new insights on early cosmic star-formation and the properties of the first stars, and show possible connections between local dwarf galaxies and more distant Damped Lyman Alpha systems.