  With the successful launch of Chandra and XMM/Newton X-ray space missions
combined with the lower-energy band observations, time has arrived when careful
comparison of thermal evolution theories of isolated neutron stars with
observations will offer a better hope for distinguishing among various
competing neutron star cooling theories. For instance, the latest theoretical
and observational developments may already exclude both nucleon and kaon direct
Urca cooling. In this way we can now have a realistic hope for determining
various important properties, such as the composition, superfluidity, the
equation of state and stellar radius. These developments should help us obtain
deeper insight into the properties of dense matter.
