The present status of quarks and leptons

Historically the search for the fundamental elements of matter has exhibited a recurring theme. Patterns are discerned that hint at substructure in the elements, and then scattering reveals the new layer of elementarity. A force is identified that binds the new constituents to build up the old 'elements' as compounds. The Pauli principle is crucial in limiting the possible structures. This is familiar for the atomic elements; it is also true for the strongly interacting 'elementary particles' built from quarks. These avenues are examined for hadrons, and evidence for quarks, gluons, and colour forces will be reviewed. The theme illustrates how the arena of elementary particle physics has progressed from hadrons to quarks and leptons. (author)