 This study used atom probe tomography and isotope tracing techniques to investigate the effects of oxygen diffusion and transport in perovskite metal heterostructures. The researchers found that annealing in 1802 gas caused elemental and isotopic redistribution in the perovskite material, while nickelchromium underwent oxidation via multiple mechanisms and transport pathways. Density functional theory calculations were conducted at experimental conditions to explain the observed reaction mechanisms and reveal the complex interplay between defects and oxygen transport. This study provides insight into the fundamental coupling of defects and oxygen transport in an important class of catalytic materials. This article was authored by Sandra D. Taylor, Kayla H. Anno, Michelle Sassy, and others.