  A dilute concentration of magnetic impurities can dramatically affect the
transport properties of an otherwise pure metal. This phenomenon, known as the
Kondo effect, originates from the interactions of individual magnetic
impurities with the conduction electrons. Nearly a decade ago, the Kondo effect
was observed in a new system, in which the magnetic moment stems from a single
unpaired spin in a lithographically defined quantum dot, or artificial atom.
The discovery of the Kondo effect in artificial atoms spurred a revival in the
study of Kondo physics, due in part to the unprecedented control of relevant
parameters in these systems. In this review we discuss the physics, origins,
and phenomenology of the Kondo effect in the context of recent quantum dot
experiments.
