Supported heterogeneous catalysts comprising nano-sized metals/metal oxides such as Cr, Ni, Co, Au, Pd, Pt and Ag dispersed on an oxide support (i.e. SiO2/Al2O3), play a central role in an industry estimated to be worth ca. 1500 billion $US/annum. They are the principle protagonists in the conversion of fractions from natural oil and gas to produce, via core catalytic processes (i.e. polymerisation, isomerisation, reduction and oxidation), a wide variety of chemicals for everyday use. A combination of dwindling supply and increasing demand on these feedstocks means it is vital that catalysts and catalytic processes operate as efficiently as possible. Optimal efficiency is normally achieved by rationalisation of structure with function and forms the basis for much catalysis research. However the characterisation performed is often incomplete and rarely performed under reaction conditions leading to contrasting conclusions as to what makes a catalyst active. This project will develop more robust structure-activity relationships by correlating how parameters that influence catalyst performance i.e. nanoparticle size, shape, redox functionality and metal-support interactions, affect and evolve in core catalytic processes of hydrogenation and oxidation. The project adopts a novel approach drawing on skills in catalyst preparation and in situ catalyst characterisation to prepare size-controlled monometallic nanoparticles, deposited on a flat oxide supports and to characterise them in operando using simultaneous time-resolved grazing incidence X-ray scattering (GIXRS) techniques. In particular small angle/wide angle grazing incidence scattering methods (GISAXS/GIWAXS) will be used although attempts will also be made to extract pair distribution function ((GI)PDF) from the data to enable a more complete characterisation of the catalyst. Such a thorough characterisation has never been previously employed and will be used to determine the salient characteristics of catalytic nanoparticles in both two-phase (hydrogenation) and three-phase (oxidation) catalytic systems. It is expected that these measurements will prove invaluable for understanding what makes a supported nanoparticle tick and an important basis for future catalyst optimisation and design.