evidence: The particle-physics breakthrough that paved the way for the Higgs boson [...] Also in 1964 came the idea of ‘spontaneous’ symmetry breaking in particle physics, followed in 1967 by the application of this idea to ‘electroweak’ symmetry breaking. Electroweak theory explains how the weak nuclear and electromagnetic forces are unified at high energies, such as those prevalent in the early Universe, but seem to us to be distinct forces mediated by particles of very different masses. Spontaneous symmetry breaking suggested the existence of the Higgs boson — a particle eventually discovered in 2012 at the Large Hadron Collider at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland. Today, asymmetries in decays of kaons and other particles being investigated at CERN and elsewhere might point the way towards new effects beyond the standard model of particle physics.