Below. In a second step of the process, the activated AgBr crystals containing silver atoms are preferentially reduced to silver metal by a chemical reducing agent in the photographic developer. The silver atoms in the activated AgBr crystal serve as a 'seed' for reduction of silver during the development process. This results in an image of the cell or tissue overlain by black silver metal spots (grains).
This procedure can be adapted for use at the EM level.
