All natural sciences benefit from the use of electromagnetic radiation to probe the phenomena of nature. From the structure of atoms and molecules to their evolution in complex system for various energy conditions, photons have been proved to be an essential tool for exploring matter in all its form. The advent of Free Electron Lasers (FEL) has allowed to perform unprecedented experiments. The properties of the FEL radiation (transverse and longitudinal coherence, brightness, pulse length and energy bandwidth) allow to perform Coherent Diffraction Imaging at a nano-scale level, non-linear spectroscopy and to probe ultra-fast phenomena in a wide set of simple and complex systems. On the the hand the FEL radiation needs to be characterised, transported and focused in order to allow the users to perform the experiments. In this thesis the FERMI beamlines (the Italian FEL) are described in detail together with the outstanding technological and scientific experimental results.
