SCIENCE - Science's breakthrough of the year: Discovery of the Higgs boson

The observation of an elusive sub-atomic particle, known as the Higgs boson, has been heralded by the journal Science as the most important scientific discovery of 2012. This particle, which was first hypothesized more than 40 years ago, holds the key to explaining how other elementary particles (those that aren't made up of smaller particles), such as electrons and quarks, get their mass.

http://www.sciencedaily.com/releases/2012/12/121220143520.ht