Cuprate high-Tc superconductors are renowned for the inextricable complexity of their electronic structure. More than 35 years after the discovery of non-conventional superconductivity in this class of oxides, a convincing picture of their special behavior is still missing. Experimental observations and theoretical hypotheses have been accumulating over the years, with scant advances in terms of clear-cut simplifications. The reason for that is in the deep entwining of charge, spin and lattice degrees of freedom that govern cuprates. Resonant X-ray scattering (elastic and, mostly, inelastic, ie RIXS) is however providing observations helpful for the simplification of the picture. In fact, by RIXS the energy scale of orbital and spin excitations were definitely assessed, in parent compounds and in superconductors. More recently, RIXS revealed elusive charge order and associated fluctuations strongly mixed with some lattice modes. The RIXS vision of cuprates can captures the full complexity by a single technique, approaching us to the microscopic origin of the transport properties both in the normal and superconducting state. After briefly introducing the key features of the technique, I will provide an overview of the RIXS results on cuprates, with an outlook to the new opportunities available at XFELs and at storage rings.