Higgs boson

The Higgs boson was discovered by the ATLAS and CMS collaborations in 2012. It is a massive, unstable particle that is predicted by the Brout-Englert-Higgs mechanism: in a nutshell this is the mechanism by which all* particles acquire mass.

* all massive particles, that is. The photon and gluon are massless, as they do not interact with the Higgs at all.