The Andreev Reflection is the key mechanism for the superconducting proximity
effect. It provides phase correlations in a system of non-interacting electrons
at mesoscopic scales, i.e. over distances much larger than the microscopic
lengths : Fermi wavelength and elastic electron mean free path. This field of
research has attracted an increasing interest in the recent years in part
because of the tremendous development of nanofabrication technologies, and also
because of the richness of the involved quantum effects. In this paper we
review some recently achieved advances. We also discuss new open questions, in
particular non-equilibrium effects and proximity effect in systems with
ferromagnetic elements.Comment: 17 pages, no figure, to appear in J. of Low Temp. Phys., proceeding
of the LT satellite conference "Electron Transport in Mesoscopic Systems",
reference list correcte