  Matter of subnuclear density in the inner crusts of neutron stars consists of
neutron-rich atomic nuclei immersed in strongly degenerate relativistic gas of
electrons and strongly nonideal liquid of neutrons. We give a brief account of
thermodynamic and kinetic properties of this matter which are greatly affected
by Coulomb and nuclear interactions (a companion paper on the outer envelopes
is astro-ph/0012316) and show how they can be studied from observations of
thermal radiation of young (age < 100 yr) neutron stars (for a discussion of
the latter possibility, see astro-ph/0012306).
