In November 1974 a dramatic revolution occurred in high-energy physics when two teams of workers independently discovered a massive subatomic particle named the J or ψmeson (Aubertet al.1974, Augustinet al.1974). Within two years the leaders of these two teams (B. Richter and S. C. C. Ting) had been awarded the Nobel Prize for physics. This alone bears testimony to the significance of the discovery. In this article I hope to be able to explain why this discovery was so significant, how it opened up a new conception of the sub-atomic world and describe some of the related discoveries and developments that have been made in the subsequent four years.