The study of the
interaction of
hadrons, produced by
introduc
ing elementary probes
into a nucleus, with the surround
ing nuclear
medium can give
insight
into two important questions. Firstly, at high energies, the production process, the time-scales connected with it, and the pre
hadronic
interactions can be studied by us
ing the nuclear radius as a length-scale. We do this here by analyz
ing data from the EMC and HERMES experiments on nuclear attenuation. Secondly, at low energies the spectral function, and thus the selfenergy of the produced
hadron, can be studied. Specifically, we analyze the CBELSA/TAPS data on
ω production
in nuclei and discuss the importance of understand
ing
in-
medium effects both on the primary production cross section and the f
inal state branch
ing ratio. In both of these studies, an excellent control of the f
inal state
interactions is essential.