The first three years of running of LHC have brought us a wealth of information : from the discovery of a scalar boson that resembles the Higgs of the SM to the exclusion of many "easy-to-discover" BSM scenarios. The quest for new physics at the LHC has now moved to a new phase where accurate predictions for both signals and backgrounds are mandatory. I illustrate how recent progress in the field of accurate MC simulations has not only changed the way predictions are obtained but also how experimentalists and theorists work together.
