  Changes of hadronic properties in dense nuclear matter as predicted by theory
have usually been investigated by means of relativistic heavy-ion reactions. In
this talk I show that observable consequences of such changes can also be seen
in more elementary reactions on nuclei. Particular emphasis is put on a
discussion of photonuclear reactions; examples are the dilepton production at
$\approx 1$ GeV and the hadron production in nuclei at 10 - 20 GeV photon
energies. The observable effects are expected to be as large as in relativistic
heavy-ion collisions and can be more directly related to the underlying
hadronic changes.
