  Collisionless shocks, that is shocks mediated by electromagnetic processes,
are customary in space physics and in astrophysics. They are to be found in a
great variety of objects and environments: magnetospheric and heliospheric
shocks, supernova remnants, pulsar winds and their nebul\ae, active galactic
nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless
shock microphysics enters at different stages of shock formation, shock
dynamics and particle energization and/or acceleration. It turns out that the
shock phenomenon is a multi-scale non-linear problem in time and space. It is
complexified by the impact due to high-energy cosmic rays in astrophysical
environments. This review adresses the physics of shock formation, shock
dynamics and particle acceleration based on a close examination of available
multi-wavelength or in-situ observations, analytical and numerical
developments. A particular emphasize is made on the different instabilities
triggered during the shock formation and in association with particle
acceleration processes with regards to the properties of the background
upstream medium. It appears that among the most important parameters the
background magnetic field through the magnetization and its obliquity is the
dominant one. The shock velocity that can reach relativistic speeds has also a
strong impact over the development of the micro-instabilities and the fate of
particle acceleration. Recent developments of laboratory shock experiments has
started to bring some new insights in the physics of space plasma and
astrophysical shock waves. A special section is dedicated to new laser plasma
experiments probing shock physics
