Angle Resolved Photoemission (ARPES) allows to measure directly the electronic band structure of crystalline solids. It is based on the photoelectric effect: the electron inside the solid absorbs energy and (negligible) momentum from the incoming photon and is ejected in vacuum where it is detected retrieving information about its initial state energy, momentum and spin. State of the art electron energy and momentum analyzers, and high energy resolution and polarization control of the exciting light are needed for resolving the fine electronic structure. Adding efficient spin-polarization measurement to ARPES, i.e. measuring Spin Polarized-ARPES at uncompromised energy and momentum resolution will enable addressing the study of the magnetic properties of surfaces, interfaces and nanostructures, as well as the spin-orbit coupling effects that determine the spin texture of the surface bands in complex materials of interest for their potential in spintronics.