  The experimental and theoretical studies of Giant Resonances, or more
generally of the nuclear collective vibrations, are a well established domain
in which sophisticated techniques have been introduced and firm conclusions
reached after an effort of several decades. From it, information on the nuclear
equation of state can be extracted, albeit not far from usual nuclear
densities. In this contribution, which complements other contributions
appearing in the current volume, we survey some of the constraints that have
been extracted recently concerning the parameters of the nuclear symmetry
energy. Isovector modes, in which neutrons and protons are in opposite phase,
are a natural source of information and we illustrate the values of symmetry
energy around saturation deduced from isovector dipole and isovector quadrupole
states. The isotopic dependence of the isoscalar monopole energy has also been
suggested to provide a connection to the symmetry energy: relevant theoretical
arguments and experimental results are thoroughly discussed. Finally, we
consider the case of the charge-exchange spin-dipole excitations in which the
sum rule associated with the total strength gives in principle access to the
neutron skin and thus, indirectly, to the symmetry energy.

Nuclear Theory;Nuclear Experiment