Emulsions stabilized by solid particles are known as Pickering emulsions. Although Pickering emulsions are encountered in various natural and industrial processes such as crude oil recovery, oil separation, cosmetic preparation, and waste water treatment, the underlying phenomena are poorly understood. The structure of self-assembled microparticles and dodecanethiol-capped silver nanoparticles was studied at Pickering emulsion interfaces using confocal microscopy and environmental transmission microscopy. Monodisperse polystyrene particles aggregated and formed small patches at the polydimethylsiloxane/water emulsion interface with local hexagonal order. Because of the relatively low surface concentration of the solid particles (∼ 0.46) at the oil-water interface, the aggregation of particles and formation of islands are likely due to the diffusion-limited cluster aggregation, which is analogous to colloidal suspensions. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).