  Solid state material at high pressure is prevalent throughout the Universe,
and an understanding of the structure of matter under such extreme conditions,
gleaned from x-ray diffraction, has been pursued for the best part of a
century. The highest pressures that can be reached to date (2 TPa) in
combination with x-ray diffraction diagnosis have been achieved by dynamic
compression via laser ablation . The past decade has witnessed remarkable
advances in x-ray technologies, with novel x-ray Free-Electron-Lasers (FELs)
affording the capacity to produce high quality single-shot diffraction data on
time scales below 100 fsec. We provide a brief history of the field of dynamic
compression, spanning from when the x-ray sources were almost always
laser-plasma based, to the current state-of-the art diffraction capabilities
provided by FELs. We give an overview of the physics of dynamic compression,
diagnostic techniques, and the importance of understanding how the rate of
compression influences the final temperatures reached. We provide illustrative
examples of experiments performed on FEL facilities that are starting to give
insight into how materials deform at ultra-high strain rates, their phase
diagrams, and the types of states that can be reached. We emphasize that there
often appear to be differences in the crystalline phases observed between use
of static and dynamic compression techniques. We give our perspective on both
the current state of this rapidly evolving field, and some glimpses of how we
see it developing in the near-to-medium term.
