Throughout history, scientists have sought to answer a fundamental question:

what are the basic building blocks of matter?

If we divide matter into smaller and smaller pieces, how far can we go?

For a long time, the atom was believed to be the fundamental, indivisible constituent of all matter. However, groundbreaking experiments in the late 19th and early 20th centuries revealed that atoms are made up of even smaller subatomic particles.

Particle physics explores matter at its most fundamental level. To probe these microscopic structures, physicists rely on powerful instruments such as particle accelerators.

The lesson below explores our modern understanding of subatomic particles through the Standard Model and examine how facilities like CERN and SLAC use particle accelerators to unveil the fundamental nature of our universe.

The Standard Model

The Standard Model of Particle Physics

For centuries, physics relied on a simple model of the atom consisting of just three subatomic particles: protons, neutrons, and electrons. However, as powerful particle accelerators and cosmic ray detectors emerged in the mid-20th century, physicists discovered dozens of new subatomic particles—creating a confusing "particle zoo."

To make sense of this complexity, physicist Murray Gell-Mann proposed the quark model in the 1960s, arranging particles by their fundamental properties. This framework evolved into the Standard Model—the definitive theory describing all known fundamental particles and the forces governing them.

The Standard Model classifies matter and energy into two primary groups:

• Fermions (Matter Particles): Quarks (which build protons and neutrons) and Leptons (such as electrons and neutrinos).
• Bosons (Force Carriers): Photons, Gluons, and W/Z bosons, which mediate fundamental forces, along with the Higgs Boson, which gives particles their mass.

Watch the video below to explore how the Standard Model categorizes matter, explains antimatter, and underpins modern particle physics.