The scanning electrochemical microscope (SECM) has been used to perform the first metal deposition on non-conducting substrates at high resolution. In a mixture of ethyleneglycol and water; hydroquinone was generated locally to reduce silver cations in the vicinity of an AgCl-coated sample. The observed mechanism of silver formation was in good agreement with published results concerning the development of photographic films. At first in a step known as "chemical development", silver cations diffusing through the AgCl crystals were discharged on their surfaces. The formed silver particles acted as metallic nuclei catalysing further discharging of the dissolved cations according to a "physical development" which became the dominant process at the sample. Under a stationary ultramicroelectrode, silver discs grew continuously and reached an apparently limiting diameter. Moreover, suitable conditions for the deposition of lines were investigated. Under appropriate conditions, the line width fell below the diameter of the tip used. This phenomenon is explained by temporary changes in the diffusion field and the reaction zone. Due to the focusing effect on the surface modifying species, the diffusion field acts as a chemical lens increasing the resolution.