Understanding the structure of catalysts under relevant reaction conditions is crucial, as their active sites often undergo dynamic changes. These transformations can significantly influence the catalytic performance, emphasizing the importance of employing operando techniques that enable real-time monitoring. This seminar will explore the application of X-ray Absorption Spectroscopy (XAS) to identify spectral signatures and molecular structures of active sites under in situ and operando conditions. XAS is particularly advantageous for such studies due to its chemical selectivity and sensitivity to the local atomic environment, offering fundamental insights into the electronic and structural properties of the investigated materials. [more]