Stellar spectroscopy is vitally important in many fields of modern astrophysics. The method allows the analysis of fundamental parameters of stars and their chemical composition, the information crucial for studies of stellar physics, star - exoplanet connection, structure and evolution of galaxies. Large surveys, such as WEAVE and 4MOST, will deliver millions of spectra of stars from the most distant corners of the Milky Way. Next-generation gigantic facilities, such as the Extremely Large Telescope (ELT), will observe stars beyond tens of megaparsecs past the Local Group. I will highlight some of the key recent advances in spectroscopy of cool stars. New models of stellar atmospheres and spectra, which account for hydrodynamics and non-local thermodynamic equilibrium, make stars look different and turn classical concepts about stellar physics, origin of the elements, and Galactic evolution upside-down. I will discuss how these developments impact our understanding of stellar explosions and of the Milky Way’s past, in particular, in relation to the emerging field of Galactoseismology. I will also discuss the potential of extragalactic stellar spectroscopy with ELT and present outlook for the future studies.