AURION R-Gent SE-EM is a high efficiency silver enhancement reagent for electron microscopy. It intensifies the gold particles by homogeneous deposition of metallic silver on the particle surface. The resulting electron dense signal is easily detected and is compatible with heavy metal counterstaining. The reagent has extremely delayed auto-nucleation and can be used under standard laboratory light conditions. It also has low viscosity, which is especially advantageous for pre-embedding immunogold applications.