The oldest, most metal-poor stars found in the Galactic halo and satellite dwarf galaxies retain in their atmospheres the chemical footprints of the high redshift Universe. Employing “stellar archaeology” – the diverse use of the chemical and dynamical properties of metal-poor stars – outstanding questions about the early Universe can be answered. Using high resolution optical and UV spectroscopic observations of the dataset of the most chemically interesting metal-poor stars, I aim to probe the nature of the first stars and supernovae explosions (SNe), the relevant nucleosynthesis processes responsible for the formation and evolution of the elements as well as early star and galaxy formation processes. I will discuss how I’ve used the most metal-poor Galactic halo stars to help elucidate the nature of their First star progenitors and mechanisms of the SNe responsible for their chemical signatures. Additionally, I will highlight recent advancements in our understanding of the heaviest elements formed via the r(apid) neutron capture process (r-process) found in metal-poor stars, especially in light of the ground-breaking gravitational wave discovery of the binary neutron star mergers event GW170817. Finally, I will show how the atmospheres of these metal-deficient stars could be used to place constraints on modeling of non-equilibrium steady-state systems, as applied to studies of stellar and planetary atmospheres.