The Standard Model of elementary particles and forces includes six quarks, which bound together to form composite particles. Physicists have an excellent understanding of how three quarks cluster together to form protons, neutrons and heavier baryons, and how a quark and anti-quark bind together to create pions, kaons and other mesons. But electron-positron colliders at SLAC National Accelerator Laboratory and the Japanese laboratory KEK have revealed examples of composite quark structures–named X and Y particles–that are not the usual mesons and baryons. Now the CDF collaboration at Fermilab has found evidence for the Y(4140) particle.