  The QCD vacuum shows the dynamical breaking of chiral symmetry. In the
hot/dense QCD medium, the chiral order parameter such as $ < \bar q q > $ is
expected to change as function of temperature $T$ and density $\rho$ of the
medium, and its experimental detection is one of the main challenges in modern
hadron physics. In this article, we discuss theoretical expectations for the
in-medium hadron spectra associated with partial restoration of chiral symmetry
and the current status of experiments with an emphasis on the measurements of
properties of mesons produced in near-ground-state nuclei.
