I will review the development of condensed matter theory since 1950 and my research in SNU for about 30 years. I explain the Kondo phenomena and many-body coherence as easy as possible. I will also discuss the present status of studying nonequilibrium Kondo phenomenon, which is one of long standing problems in condensed matter theory. Recently, many two-electrode mesoscopic devices attract our interest. They are quantum point contacts, Kondo atom adsorbed on a metallic substrate, single-electron transistors, doped grapheme, and so on. The dI/dV lineshapes observed for these systems are not understood yet. That is because the strongly correlated system under bias has not been studied successfully. I show my developments on this emerging field.