Nuclear emulsions in the OPERA experiment

The use of emulsions as particles detector has a long and successful life. The recent development of fast automatized analysis systems has allowed the use of huge amount of emulsions films with no precedence in the history of particle physics. The OPERA experiment, running in the underground Laboratori Nazionali del Gran Sasso (LNGS), for the confirmation of the neutrino oscillation in the $\nu_{\mu}\to\nu_{tau}$ channel, is "the major" of these experiments. The experimental technique, the strategy and the first results of the experiment are presented.