OPERA: An appearance experiment to search for nu(mu) --> nu(tau) oscillations in the CNGS beam

This article reviews the status of the OPERA experiment. The OPERA experiment is dedicated to the appearance search of nu_mu into nu_tau oscillations in the parameter region indicated by Super-Kamiokande data. OPERA is a long baseline experiment located at the Gran Sasso Laboratory in the CNGS neutrino beam from the CERN SPS. The detector design is based on a massive lead/nuclear emulsion target. Electronic detectors locate the events in the emulsions. Magnetised iron spectrometers measure charge and momentum of muons. The discovery potential of OPERA originates from the observation of a nu_tau signal with very low background level. The direct observation nu_mu into nu_\tau appearance will constitute a milestone in the study of neutrino.