The combination of in situ with online catalytic studies can have a great impact on research and development in het-erogeneous catalysis, since they can provide direct insight into the active state of a catalyst. In operando studies, where the experiments for catalyst testing and spectroscopic measurements are combined, the design of the cell is of crucial importance for simultaneously obtaining activity and spectroscopic information. We present here the applica-tion of microfabricated reactors for studies of silver catalyst in the oxidation of methanol to formaldehyde using X-ray absorption and Raman spectroscopy under reaction conditions. The microreactors used in this work were made of silicon and glass and were fabricated by photolithography and anodic bonding. Silver catalyst was incorporated by sputter coating before anodic bonding. The microreactors were placed in appropriate heating units for X-Ray absorp-tion and Raman measurements. In a typical experiment, the microreactor assembly was connected to a gas control manifold, through which oxygen or methanol containing reaction gas mixtures were introduced. In the operando Raman study, the reaction products were analysed online by a gas chromatograph. In situ X-ray absorption spectro-scopic studies were performed at the silver K-edge, of the silver catalyst deposited in the reaction channel of the mi-croreactor cell. The as-prepared catalyst showed that only metallic silver phase was present. Analysis of the EXAFS data recorded during calcination at 773K in air, indicated that some of the silver metal was oxidized. Upon introduc-tion of the methanol/air mixture, contribution due to Ag-O appeared to decrease slightly and correspondingly the Ag-Ag contribution was seen to increase. Operando Raman-GC studies indicated the presence of an atomic surface oxy-gen species at 810cm-1 under oxygen, which disappeared upon the introduction of the reaction mixture. Various oxy-gen species (most probably subsurface) gave rise during reaction to a broad complex feature at 400-800cm-1, and their presence was associated with high formaldehyde selectivity. Carbon deposition was observed when a feed without water was introduced into the reactor, resulting to decreased methanol conversion with reaction time. Modelling studies confirmed the isothermal, plug-flow behaviour of the microreactor which facilitated the analysis of kinetic data.