  Gamma-Ray Bursts (GRBs) are extra-galactic and extremely energetic transient
emissions of gamma rays, which are thought to be associated with the death of
massive stars or the merger of compact objects in binary systems. Their huge
luminosities involve the presence a newborn stellar-mass black hole emitting a
relativistic collimated outflow, which accelerates particles and produces
non-thermal emissions from the radio domain to the highest energies. In this
article, I review recent progresses in the understanding of GRB jet physics
above 100 MeV, based on Fermi observations of bright GRBs. I discuss the
physical implications of these observations and their impact on GRB modeling,
and I present some prospects for GRB observation at very high energies in the
near future.
