Abstract : Solid state sintering of powders is investigated by miscellaneous experimental and modelling methods. Densification kinetics of several systems based on copper powders is first measured by dilatometry. These materials are next observed by in situ microtomography at Grenoble synchrotron. From a quantitative analysis of the 3D images obtained, the parameters characterizing their microstructural changes are followed throughout sintering. Modelling of the sintering of the same materials are finally achieved with dp3D discrete element code, which simulates random assemblies of particles interacting at the contacts between each other. The conjunction of experimental and numerical allows evaluating the influence of collective phenomena, as rearrangement, in relation with material heterogeneities (particle size distribution, packing defects, and inert inclusions) on the sintering process.