The contribution of Quasars and Galaxies to the UV background

After more than thirty-five years the issue of the sources driving the reionization of the hydrogen in the Universe and keeping it ionized afterward does not appear to be settled. It is commonplace that galaxies are able to produce the bulk of the UV emissivity at high redshift, but the AGN population is also proposed as a major or dominant contributor. In this talk we discuss observations aiming to a more precise assessment of the role played by different types of sources across the cosmic history and of the so-called photon underproduction crisis in the local Universe.