  Non-uniform structures of nuclear matter are studied in a wide density-range.
Using the density functional theory with a relativistic mean-field model, we
examine non-uniform structures at sub-nuclear densities (nuclear ``pastas'')
and at high densities, where kaon condensate is expected. We try to give a
unified view about the change of the matter structure as density increases,
carefully taking into account the Coulomb screening effects from the viewpoint
of first-order phase transition.
