Andreev reflection and proximity effect

The Andreev Reflection is the Ley mechanism for the superconducting proximi ty effect. It provides phase correlations in a system of non-interacting el ectrons at mesoscopic scales, i.e. over distances much larger than the micr oscopic lengths : Fermi wavelength and elastic electron mean free path. Thi s field of research has attracted an increasing interest in the recent year s in part because of the tremendous development of nanofabrication technolo gies, and also because of the richness of the involved quantum effects. In this paper we review some recently achieved advances. We also discuss new o pen questions, in particular non-equilibrium effects and proximity effect i n systems with ferromagnetic elements.