Rare Flavour Changing Neutral Currents (FCNC) decays can proceed in Standard Model (SM) only through loop processes. For that reason they are a powerful tool to test the quantum structure and the flavor sector of the SM and, at the same time, they are sensitive indirect probes of New Physics (NP) effects beyond the SM. In particular they provide information on the couplings and masses of heavy intermediate states appearing inside the loops and allow to explore energy scales well above the ones reacheable with direct searches. The latest results on rare decays of beauty and charm hadrons obtained from the LHCb experiment with data collected during the first run of the LHC will be presented in this talk.