  Thermal surface emissions have now been detected from more than a dozen
isolated neutron stars, including radio pulsars, radio-quiet neutron stars and
magnetars. These detections can potentially provide important information on
the interior physics, magnetic fields, and surface composition of neutron
stars. Understanding the properties of matter and radiative transfer in strong
magnetic fields is essential for the proper interpretation of the observations.
We review current theoretical works on modeling magnetized neutron star
atmospheres/surface layers, discussing some of the novel properties of matter
and radiative transfer in strong magnetic fields. Of particular interest is the
effect of the strong-field vacuum polarization, which dramatically changes the
radiative transfer and the emergent X-ray spectra from magnetars.
