  We demonstrate a tunable Kondo effect realized in small quantum dots. We can
switch our dot from a Kondo impurity to a non-Kondo system as the number of
electrons on the dot is changed from odd to even. We show that the Kondo
temperature can be tuned by means of a gate voltage as a single-particle energy
state nears the Fermi energy. Measurements of the temperature and magnetic
field dependence of a Coulomb-blockaded dot show good agreement with
predictions of both equilibrium and non-equilibrium Kondo effects.
