[en] Free Electron Lasers are new sources of tunable coherent radiation, based on the interaction of a relativistic electron beam with a permanent magnetic field. The FEL implemented on the Super-ACO storage ring at Orsay started to operate in the visible in 1989 at 600 MeV. Nowadays, the FEL operates in the UV (down to 300 nm) at 800 MeV, the nominal energy of the electron beam, with a compatibility with synchrotron radiation users exploiting the temporal structure, at high repetition rate (8 MHz). It presents a high average laser extracted power (up to 300 mW), short pulses (15-50 ps FWHM) and small bandwidth (0.2 nm). A longitudinal feedback system allows to reduce the FEL micropulse jitter to a few ps, the wavelength drift down to 0.01 A and the intensity fluctuations down to 1 %. Taking advantage of these performances, it was demonstrated for the first time the feasability of using a storage ring FEL and a FEL in the UV as a coherent source of radiation for scientific applications. Time-resolved fluorescence and anisotropy decays of an coenzyme in solution were measured, leading to the identification of two conformational states in thermodynamical equilibrium in solution. Moreover, the implantation of the FEL on a storage ring naturally leads to develop pump-probe two-color experiments for the study of the dynamics of excites states, because of the natural synchronization between synchrotron radiation and the FEL. First experiments were started in surface physics, for the study of the surface photovoltage effect at the interface of semiconductors and metals. The Super-ACO FEL is also combined to the white (visible, near UV) synchrotron radiation for transient absorption experiments on chemical and biological species in solution. Two-color temporal effects were measured on a dye and studies are actively carried out on the acrinide. Again, the UV FEL induced transformation of chemical bounds of kaolinite was probed with the infra-red microscopy with synchrotron radiation. The tunable Super-ACO FEL source, combined with synchrotron radiation covering the X-ray to infra-red range, is a unique tool for the time dependent studies on excited states. It benefits from the natural synchronisation of both sources at a high repetition rate, their mutual tunability, high intensity and coherence. Several experimental set-ups are now under operation. (author)