High energy Cosmic rays are a unique window to explore Particle Physics at energies scales well above those reached by Man made accelerators. This window has been exploited by a new generation of large cosmic rays experiments, namely the Observatory Pierre Auger. Recently, a set of results, some of them not easily explained in the framework of current hadronic interaction models, have been published. In this colloquium the present and the future of this field will be reviewed and discussed.