Preface

I review the main features and some of the theoretical attempts to explain the excess around an invariant mass of 750 GeV seen in 2015 at the LHC in the di-photon channel. As this hint to new physics has now all but disappeared from the higher-luminosity 2016 data, the statistical analysis nicely illustrates why only a high level of significance can be trusted in a discovery. The various explanations that has been suggested remain interesting examples of our current understanding of physics beyond the standard model and also of the challenging task of discriminating among them.