The structure of Au nanoparticles supported on CeO2 using the deposition precipitation method was observed using a transmission electron microscope (TEM). The shape of Au nanoparticles and the fine structure of contact interface between the Au nanoparticles and CeO2 supports were carefully examined. It was found that there was a preferential orientation relationship between Au nanoparticles and the CeO2 support. It was also observed that small and thin Au nanoparticles disappeared during TEM observation, shrinking layer by layer down to a mono-atomic layer. (c) 2005 Springer Science + Business Media, Inc.