In this talk, I will present recent advances in our understanding of the history of Galactic nucleosynthesis, driven by new observational data and improved stellar modelling. A key focus will be on insights into stellar chemical abundances made possible by state-of-the-art 3D radiation-hydrodynamics stellar atmospheres and non-local thermodynamic equilibrium (NLTE) spectral models. These results are part of the multidisciplinary series of studies Observational Constraints on the Origins of the Elements, which aims to provide a comprehensive framework for tracing the Galactic evolution of elemental abundances—from the lightest species (C and O), through the α-elements and Fe-peak elements, to the products of s- and r-process nucleosynthesis. I will present our 3D NLTE findings on the evolution of Fe-peak elements and discuss their significance for understanding core-collapse supernovae (CCSNe), Type Ia supernovae, and their progenitors. I will then explore neutron-capture element abundance ratios in the context of asymptotic giant branch (AGB) stars and neutron star mergers. The talk will conclude with a forward-looking perspective on extragalactic nucleosynthesis, emphasising the opportunities enabled by next-generation facilities such as JWST and the ELT.