At the deepest level of matter, we meet the quarks — fundamental particles that always come in groups. A proton contains two up quarks and one down quark; a neutron has two downs and one up. These quarks are bound so tightly by the strong force that they can never escape individually. This bond is maintained by massless particles called gluons, which act like elastic bands snapping between the quarks.

Quarks carry a unique kind of charge called color charge, which has nothing to do with visible color but represents how the strong force works. The rule is simple: only “color-neutral” combinations — one red, one green, one blue — can exist in nature. If you try to separate quarks, the field between them stretches like a rubber band until it breaks — and the energy used creates new quark pairs. This process is called confinement.

There are six types, or flavors, of quarks: up, down, strange, charm, top, and bottom. The heavier ones exist only fleetingly in high-energy collisions, but up and down quarks make up nearly everything around us. Interestingly, most of a proton’s mass does not come from the quarks themselves but from the intense energy of the gluon field that binds them — proof that mass can arise from pure energy. Quarks are the foundation of all matter, but their dance with gluons is what gives the universe its weight.