A deep understanding of the atomistic mechanisms underlying different energy-related chemical processes requires recording large datasets under operando conditions, yielding key information about the working material. Therefore, the desired parameters to study include the chemical composition at the interface and bulk, the chemical states of the atoms and their variations resulting from the reactions, as well as the structural evolution. Unfortunately, the analytical techniques capable of providing information under reaction conditions are very limited since the complex environments often required for running the reaction are hardly compatible. Consequently, in many cases, only ex situ characterizations are feasible, leading to a loss of important information because the intermediates and active species cannot be “quenched” for post-process analysis. As a result, in situ/operando characterization has gained significant attention in recent years. X-ray characterization techniques provide bulk-to-surface information in an element-specific manner, which is usually not possible with other characterization techniques. However, these techniques, especially those based on photoelectrons, are not easily compatible with complex environments such as gases and liquids, requiring ultra-high vacuum for operation, particularly in the soft X-ray regime. This symposium will focus on the in situ and operando techniques developed for the investigation of energy materials under relevant working conditions using X-ray techniques.