Magnetic Impurities in conductors alter the Fermi sea: A many-body state (A Kondo singlet) is formed that entangles itinerant carriers and the impurity site. This causes a sharp rearrangement of the density of states near the Fermi surface into a hierarchical set governed by a single energy parameter Tk, the Kondo temperature. Equilibrium physics of such electronic "knots" scales with Tk and is highly universal: impuritites that differ microscopically from one another yet have similiar Kondo temperatures produce Kondo states with similar properties. Recent studies of Kondo physics with voltage-controllable spin traps known as Single-Electron Transistors (SETs) have focused on nonequilibrium Kondo phenomena, sensitive to the interplay between coherent correlations and dissipative effects, aiming to understand the extent of Kondo university away from equilibrium
