2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189846In these lectures I first give a motivation for investigations of in-medium properties of hadrons. I discuss the relevant symmetries of QCD and how they might affect the observed hadron properties. I then discuss at length the observable consequences of in-medium changes of hadronic properties in reactions with elementary probes, and in particular photons, on nuclei. Here I put an emphasis on new experiments on changes of the sigma and omega mesons in medium.Lecture at "Workshop on Hadron Physics", Puri, India, March 7 - 17, 2005Nuclear Theorytext