What do we learn from Resonance Production in Heavy Ion Collisions?

Resonances with their short life time and strong coupling to the dense and hot medium are suggested as a signature of the early stage of the fireball created in a heavy ion collision \cite{rap00,lut01,lut02}. The comparison of resonances with different lifetimes and quark contents may give information about time evolution and density and temperature of during the expanding of fireball medium. Resonances in elementary reactions have been measured since 1960. Resonance production in elementary collisions compared with heavy ion collisions where we expect to create a hot and dense medium may show the direct of influence of the medium on the resonances. This paper shows a selection of the recent resonance measurements from SPS and RHIC heavy ion colliders.