Launched in March 2024, Advanced Characterizations and Optimized Functional Materials for Energetic Transition focuses on the characterization of material, both individually andwithin the devices in which they will be used. The Research Unit also develops new in-situ/operando characterization approaches, which are key techniques for designing optimized functional materials. Specifically, the observation of such materials while they work in simulated-device conditions, through e.g., transmission electron microscopy, X-ray diffraction, Raman and IR spectroscopies, X-ray photoelectron spectroscopy, will help shed light into reaction mechanisms and materials modification. The strategies employed will help clarify how catalysts change during electrochemical activity and whether the material is suitable for its intended application.