The Standard Model: Quarks and Leptons

For centuries, scientists searched for the fundamental building blocks of matter — particles that cannot be broken down any further. By the mid-twentieth century, physicists had discovered a bewildering zoo of subatomic particles in cosmic rays and particle accelerators. The Standard Model of particle physics, developed through the 1960s and 1970s, brought order to this chaos by identifying a small set of truly fundamental particles from which everything else is built.

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Fundamental Particles

A fundamental (elementary) particle is one that has no internal structure — it is not made of anything smaller. The Standard Model contains two families of fundamental matter particles: quarks and leptons. Both families contain six particles, organised into three generations.

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Quarks

Quarks are the fundamental particles that make up protons, neutrons, and other hadrons. They come in six flavours, arranged in three generations: