  Renormalization group theory of the Kondo effect predicts that an impurity
spin is screened by a conduction electron spread over a large distance of order
>.1 to 1 micron. This review has the following sections: 1. The Kondo effect
and the screening cloud, 2. Non-observation of the Kondo cloud in conventional
experiments, 3. Kondo effect in transmission through a quantum dot, 4.
Observing the screening cloud in persistent current experiments, 5.
Side-coupled quantum dot, 6. Conclusions
