Quark
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.
KLOE (experiment)
Data from the original experiment allowed Makoto Kobayashi and Toshihide Maskawa to give the most precise measurement of one of the elements of the quark mixing matrix currently available. They then used this value to discover "the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature", which won them the Nobel Prize in Physics in 2008.