1 | P a g e Solid-state chemical reactions occur across multiple length scales, ranging from large-scale geological transformations within the Earth's crust to the precise micro/nano-scale engineering of materials . A variety of intricate physical and chemical processes are pronounced at elevated temperature due to enhanced chemical transport and accelerated kinetics, including hightemperature oxidation and corrosion, temperature-induced mechanical stresses, elastic/plastic deformations, and phase transformations . A key driving force behind many of these processes is the chemical transport of active elements and compounds across interfaces . Controlling the chemical dynamics at micro-to nanometre length scales via temperature plays a central role in tailoring the properties, performance, and stability of materials and multi-material structures . To this end, tracking changes in real time at commensurate length scales is paramount for providing crucial feedback to guide the design of materials, such as by identifying the temperature range at which desirable properties emerge or at which chemical products are formed, and for understanding the underlying mechanisms of solid-state reactions.