Understanding material behavior under realistic operating conditions is essential for advancing sustainable energy technologies. This symposium will focus on recent advances in lab-based in situ and operando characterization techniques applied to energy conversion systems spanning across batteries, solar cells, and (photo)electrochemical devices. While relying on shared fundamental processes – governed by material composition, interfaces, defects, and transport of charged particles – these systems are often studied using only discipline-specific methods. By bringing together researchers from diverse fields within energy conversion, this symposium aims to promote and facilitate cross-disciplinary exchange and to identify shared challenges and innovative solutions. Emphasis will be placed on emerging lab-based techniques that probe composition, structure, optoelectronic properties, and ionic/electronic transport, where studies offering spatial and temporal resolution are particularly encouraged. These studies are crucial for understanding reaction mechanisms and degradation within complex conversion processes, ultimately enabling the rational design of more efficient and durable energy materials.