Recent advances in in situ and operando X-ray spectroscopy have transformed our ability to visualize how surfaces and interfaces evolve under realistic working conditions. By combining X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), these techniques offer direct, molecular-level insights into the coupled structural, chemical, and electronic processes that govern energy conversion and storage. In this talk, the role of synchrotron-based in situ and operando X-ray spectroscopy will be highlighted as a unified framework for understanding the dynamic interplay between surface chemistry and electronic structure in a wide range of functional materials including oxide heterostructures, single atom catalysts, and lithium based electrodes. Through representative examples such as SrRuO3/SrTiO3 [1-2], RhCu single-atom alloys [3], and Li1+xTM1-xO2 lithium-rich layered oxides [4], the correlation between interfacial redox reactions, atomic scale interactions, and oxygen coordination environments will be discussed in the context of how they dictate reactivity, selectivity, and reversibility. Collectively, these studies demonstrate how in situ and operando X-ray spectroscopy bridges the gap between model systems and real materials, providing fundamental insights essential for designing next-generation catalysts and electrodes for sustainable energy technologies.