The road to iron leads through ⁵⁶Ni

A brief review is presented of the observational and theoretical evidence for the production of iron peak nuclei in explosive nucleosynthesis, for which, under proton-rich conditions, nuclei of mass A = 56 are synthesized predominantly as ⁵⁶Ni. Guided by the pioneering hydrodynamic studies of Stirling Colgate and his collaborators, it has now been firmly established that the timescale on which nuclear burning proceeds in the wake of a supernova shock wave is too short to permit any significant change (increase) in the total ratio of neutrons to protons. This guarantees dominance of the isotope ⁵⁶Ni in the iron peak nuclei emerging from explosive/supernova environments, and holds important implications for the light curves of both Type I and Type II supernovae. Current models of nucleosynthesis in supernovae predict interesting and distinguishing abundance patterns that are found to be consistent with the stellar abundance determinations of halo and disk stars in our Galaxy.