MODEL RELEASED. OPERA neutrino experiment results being studied with a microscope. OPERA (Oscillation Project with Emulsion-tRacking Apparatus) is part of the Gran Sasso National Laboratory (LNGS), inside the Gran Sasso mountain, Abruzzo, Italy. The mountain shields the LNGS experiments from outside radiation, allowing particle physicists and astrophysicists to study rare interactions involving neutrinos and other particles. OPERA studies nuclear emulsions made of micro-crystals of silver halides (AgBr) dispersed in a gelatin layer. The path of an ionizing particle is visible as sequence of black silver grains.