In this lecture I will present HFML-FELIX, a world-class research facility for matter under extreme conditions. We use high magnetic fields and high intensity terahertz radiation in combination with other parameters such as temperature and pressure, and the world-unique combination of high magnetic fields and terahertz radiation to unravel fundamental properties of matter. HFML-FELIX have a large international user community. Access to the facilities is granted, if the research proposal is positively rated by an international committee. Our installations require unique, custom-made, high quality components, designed in-house, externally or in strong collaboration with external partners and produced by industrial partners.