The characterization methods available at today’s synchrotron light sources are ideally suited to unravel the complexity of a practical working catalyst. This will be illustrated using examples from our work using a combination of synchrotron techniques including: (i) X-ray micro- and nano-tomography, (ii) X-Ray microprobe fluorescence and X-ray microprobe absorption fine structure (XAFS), and (iv) in situ XAFS combined combined with density functional theory (DFT) and DFT/MD calculations. Indeed, the use of in situ XAFS is now an integral catalyst characterization technique at UOP. The method provides detailed element-specific atomic-level structural and chemical information of the active catalyst. Often this information cannot be obtained by any other method. We have developed and implemented the appropriate equipment to allow these in situ studies to be performed. This equipment ranges from a plug flow reactor that operates at high pressure, to equipment that allows rapid collection of XAFS data from multiple samples simultaneously. These reactors are coupled to an automated gas manifold combined with on-line product analysis. Examples of our recent work will be presented. Each example will highlight a different aspect of the use of in situ XAFS in an industrial research environment. These examples will include in situ sulfidation of experimental hydroprocessing catalysts, and operando XAFS of rhenium-based catalysts. The talk will end with a look to the future.