International audienceCollisionless shocks are ubiquitous in the Universe and are held responsible for the production of non-thermal particles and high-energy radiation.In the absence of particle collisions in the system, theoretical works show that the interaction of an expanding plasma with a pre-existing electromagnetic structure (as in our case) is able to induce energy dissipation and allow for shock formation. Shock formation can alternatively take place when two plasmas interact, throughmicroscopic instabilities inducing electromagnetic fields which are able in turn to mediate energy dissipation and shock formation. Using our platform where we couple a fast expanding plasma induced by high-power lasers (JLF/Titan at LLNL and LULI2000...