Jour inhabituel !
Gamma-ray bursts (GRBs) are associated with the collapse and explosion of stellar objects. They are so bright that their observations have led to a number of important discoveries regarding different physical processes and astrophysical objects. In the last few years, GRBs have been used to investigate the nature of extremely faint and/or extremely distant galaxies, and the cosmic chemical evolution. My talk will focus on these issues and the most recent results reached thanks to the existence of GRBs.