Particle Physicists study matter at is smallest scale and try to reveal how the physical world is constructed from elementary particles and the forces acting between them. The well-known proton, neutron and similar particles are composed of quarks. Atoms also contain electrons; together with the two heavier versions of the electron (the muon and tau), each with its associated neutrino, they make up the group of leptons. Another ingredient of the catalogue of particles is the Higgs boson, discovered at the CERN Lab's Large Hadron Collider (LHC) in 2012.