Gamma-Ray-Bursts and High-Energy-Cosmic-Rays are two of the most intriguing enigmas of astrophysics. A promising scenario solving both problems consists in the Fermi-like acceleration of particles by relativistic collisionless shocks. These shocks could generate the Gamma Burst together with some highly energetic cosmic rays, in the earlier phase of a Supernovae explosion. Later on, the Supernovae Remnant could still accelerate cosmic rays at lower energies. At any rate, the very birth of the shock, and the subsequent acceleration process, rely heavily on the electromagnetic instabilities triggered when a relativistic beam passes through a plasma. Recent progresses regarding these issues will be reviewed.