  Generic properties of the strength function (local density of states (LDOS))
and chaotic eigenstates are analyzed for isolated systems of interacting
particles. Both random matrix models and dynamical systems are considered in
the unique approach. Specific attention is paid to the quantum-classical
correspondence for the form of the LDOS and eigenstates, and to the
localization in the energy shell. New effect of the non-ergodicity of
individual eigenstates in a deep semiclassical limit is briefly discussed.
