The research of Riccardo Rattazzi and his group focusses on the open problems in the present understanding of fundamental physics. One main issue concerns the origin of the observed four fundamental forces (gravity, electromagnetism, the weak force and the strong force) and their possible unification into a single dynamical principle. A related question concerns the mechanism of electroweak symmetry breaking and the origin of the observed mass hierarchies. Another class of questions arises from cosmological observation. Here one stark difficulty is represented by the mysterious dark matter, which certainly cannot be accounted by the known particles. More conceptual, but formidable, issues are the cosmological constant problem and the construction of a realistic theory of the early universe. Quite possibly some of the above questions have a common answer, as for instance exemplified by an intriguing connection between dark matter and the electroweak scale. Also, quite excitingly, the above list of questions will almost surely be reshaped in the forthcoming years by data from the Large Hadron Collider (LHC) and from several dark matter detection experiments. The past research of Riccardo Rattazzi has been mostly carried out from the particle physics standpoint. He has worked on ideas like supersymmetry, grand-unification or extra-dimensions, also studying their broad phenomenological implications. He is the co-discoverer of a subtle quantum effect in supergravity which could play an important role in the generation of a mass for the supersymmetric particles. More recently he has been applying effective field theory methods to better define what is possible and what is not in cosmological evolution.