INSTANTON-INDUCED EFFECTS IN QCD

The review starts with a few puzzles related to the scales at which the perturbative description should be replaced by a non-perturbative one. A number of various examples are considered, leading to different scales and eventually related to instantons (or confinement) effects. Then we discuss the QCD vacuum as an instanton liquid, and show that statistical models based on this picture work surprisingly well and quantitatively explain many properties of hadrons. Then we proceed to a wider range of questions, related to the phase diagram of QCD, at finite temperature and density, emphasizing recent progress in color superconductivity. Finally, we discuss a few recent application of instanton-induced effects in high energy processes.