"Particle and radiation beams are commonly used in our daily life. For example, accelerated electrons are deflected in the cathode tube of televisions or computer screens. X rays are routinely used for non destructive material or body inspection, for example to check human bodies (to visualize tumour cells, dental caries and osseous fractures) or to increase the safety of travellers by inspecting their luggage. Ionizing radiations are efficiently used in radiotherapy to cure cancer by damaging irreversibly the DNA of cells. From the fundamental point of view, the development of ultra short bunches of energetic particles and X ray photons is of crucial importance in biology, chemistry, and solid state physics, where these beams could be used to diagnose the electronic, atomic or molecular dynamics with unprecedented, simultaneous time and space resolution. The interaction of laser beams with matter in the relativistic regime has permitted to demonstrate new approaches for producing energetic particle beams, thanks to the tremendous electric fields that plasmas can support. The incredible progress of laser plasma accelerators has allowed physicists to produce high quality beams of energetic radiation and particles. These beams could lend themselves to applications in many fields, including medicine (radiotherapy, and imaging), radiation biology, chemistry (radiolysis), physics and material science (radiography, electron and photon diffraction), security (material inspection), and of course accelerator science. Stimulated by the advent of compact and powerful lasers, with moderate costs and high repetition rate, this research field has witnessed considerably growth in the past few years, and the promises of laser plasma accelerators are in tremendous progress. The PARIS ERC/AdG proposal aims at developing actively this new field of research which is of major interest for a broad scientific community and which has the potential to provide new societal applications."