  Recent experiments studying the meson-nucleus interaction to extract
meson-nucleus potentials are reviewed. The real part of the potentials
quantifies whether the interaction is attractive or repulsive while the
imaginary part describes the meson absorption in nuclei. The review is focused
on mesons which are sufficiently long-lived to potentially form meson-nucleus
quasi-bound states. The presentation is confined to meson production off nuclei
in photon-, pion-, proton-, and light-ion induced reactions and heavy-ion
collisions at energies near the production threshold. Tools to extract the
potential parameters are presented. In most cases, the real part of the
potential is determined by comparing measured meson momentum distributions or
excitation functions with collision model or transport model calculations. The
imaginary part is extracted from transparency ratio measurements. Results on
$K^+, K^0, K^-, \eta, \eta^\prime, \omega$, and $\phi$ mesons are presented and
compared with theoretical predictions. The interaction of $K^+$ and $K^0$
mesons with nuclei is found to be weakly repulsive, while the $K^-,
\eta,\eta^\prime, \omega$ and $\phi$ meson-nucleus potentials are attractive,
however, with widely different strengths. Because of meson absorption in the
nuclear medium the imaginary parts of the meson-nucleus potentials are all
negative, again with a large spread. An outlook on planned experiments in the
charm sector is given. In view of the determined potential parameters, the
criteria and chances for experimentally observing meson-nucleus quasi-bound
states are discussed. The most promising candidates appear to be the $\eta$ and
$\eta^\prime$ mesons.
