Recently, I wrote a research report (http://ojs.ujf.cas.cz/~krizek/Vector_Mesons/QCD_v1002.pdf)
which deals with nowadays frequently discussed questions concerning changes of properties of vector mesons in hot and dense nuclear matter. It gives to the reader a brief overview on theoretical models describing vector mesons in nuclear medium. Further, some interesting results from experiments studying di-lepton signal in nucleus-nucleus reactions are shown.