  Muon colliders and neutrino factories are attractive options for achieving
the highest lepton-antilepton collision energies and the most precise
measurements of the parameters of the neutrino mixing matrix. The performance
and cost of these future facilities depends sensitively on how well a beam of
muons can be cooled. The recent progress of muon-cooling prototype tests and
design studies nourishes the hope that such facilities can be built during the
next decade.
