Gamma-Ray Bursts, new cosmological beacons
  Long Gamma-Ray Bursts (GRBs) are the brightest electromagnetic explosions in the Universe, associated to the death of massive stars. As such, GRBs are potential tracers of the evolution of the cosmic massive star formation, metallicity, and Initial Mass Function. GRBs also proved to be appealing cosmological distance indicators. This opens a unique opportunity to constrain the cosmic expansion history up to redshifts 5-6. A brief review on both subjects is presented here. 
V. Avila-Reese (1), C. Firmani (1,2), G. Ghisellini (2), J. I. Cabrera   (1) ((1)IA-UNAM, Mexico; (2) INAF-OAB, Italy)