Abstract: The structure and distribution of the silver particles in receiving layer in instanto-photography have been directly observed by high voltage electron microscopy. The aggregates of the silver particles in receiving layer in the presence of toner have been clearly seen. This proves that the function of the toner is to induce rapid formation of small particles and then which collect rapidly to aggregates.Silver covering power and properties of nucleus of receiving layer which relate to silver particles structure and distribution of receiving layer have been studied respectively.