  This lecture note reviews a variety of transport and thermodynamic
measurements of electron decoherence time in low-dimensional conductors at low
temperature. The mechanism of dephasing by electron interaction mediated by an
arbitrarily small number of magnetic impurities is neither applicable to our
linear-response measurements of weak localization, nor is it observed in the
recent high-field measurements of the decoherence time in nominally pure
quasi-one dimensional gold wires. The source of decoherence, after extensive
experiments, still appears to be intrinsic.
