High power laser beams are unique in concentrating energy both in space and time. They can convert dense matter into plasma of extreme energy density. Here I shall focus on two outstanding applications. Laser fusion relies on isentropic compression of nuclear fuel by convergent hydrodynamic flow, and I discuss the gas dynamics underlying ignition. Laser accelerators depend on relativistic laser plasma interaction, generating non-neutral plasmas and accelerating fields in the range of TV m−1. Self-organizing plasma structures such as channels and bubbles drive intense particle beams. Such beams may allow for fast ignition of inertial confinement fusion.