Understanding how batteries operate and degrade is critical for developing next-generation energy storage technologies. We use operando and in situ techniques, including XRD, Raman spectroscopy, NMR, optical microscopy, and electrochemical analysis, to monitor structural, chemical, and transport processes in real time. By combining advanced characterization with custom-designed operando cells, we uncover reaction mechanisms, identify performance bottlenecks, and guide the rational design of improved battery materials and systems.