The merits of employing combined in situ X‐ray absorption spectroscopy (XAS) and X‐ray diffractometry (XRD) are described by reference to a number of examples, which encompass: (i) crystallisation of molecular sieve catalysts; (ii) determination of the atomic architecture of active sites in CoALPO and MnALPO catalysts; (iii) the thermal stability and change of structure in the immediate vicinity to (and at a distance away from) transition‐metal‐ion active sites in microporous catalysts; (iv) subtle changes in electronic state (of copper active sites) in hydrotalcite‐based catalysts for $${\text{NO}}_x $$ elimination; (v) charting the entire cycle of preparation, use and regeneration of isolated Ti(IV)‐centred active sites on mesoporous silica supports for the epoxidation of alkenes; and (vi) characterising the nature of bimetallic and other active cluster catalysts supported on silica. Recent developments in technique, notably the merits of energy‐dispersive X‐ray diffraction (which permit in situ studies with the use of stainless steel containers) are also highlighted.