[en] Analytical electron microscopy characterization techniques have been developed to investigate the structural features of small metal particles (50 to 100 angstroms) in porous media. In the first phase of the project, bright and dark field imaging techniques have been emphasized with EDAX characterization. High quality images have been obtained in both bright field and dark field and earlier characterization studies on three catalyst systems have been confirmed and extended. Particle size growth (sintering) at low temperatures is much greater in the Au/SiO₂ system, indicating a weak metal-support interaction. A more uniform and generally smaller particle size distribution is observed in Ni/MgSiO₃ compared to Ni/SiO₂. The nickel particles in Ni/SiO₂ show contrast effects which indicate that the particles contain faults or twins