  The behavior of the electron dephasing time near zero temperature,
$\tau_\phi^0$, has recently attracted vigorous attention. This renewed interest
is primarily concerned with whether $\tau_\phi^0$ should reach a finite or an
infinite value as $T \to$ 0. While it is accepted that $\tau_\phi^0$ should
diverge if there exists only electron-electron (electron-phonon) scattering,
several recent measurements have found that $\tau_\phi^0$ depends only very
weakly on temperature, if at all, when $T$ is sufficiently low. This article
discusses the current experimental status of "the saturation problem", and
concludes that the origin(s) for this widely observed saturation are still
unresolved.
