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How are protons and neutrons made of quarks?

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Bohr model diagram of a hydrogen atom showing a green nucleus labeled H, a single electron orbit, and text with atomic mass 1.008 and electron configuration 1. — atom The Bohr model describes the structure of atoms, in this case hydrogen.

Protons and neutrons are not elementary particles; rather, they are composite hadrons built from smaller, fundamental particles called quarks.1

These quarks are held together within protons and neutrons by the strong force, which is mediated by the exchange of massless gauge bosons known as gluons. Quarks carry a property called "colour charge," and the strong force ensures that they only combine in ways that result in a net colour charge of zero.2

The specific composition of these particles is as follows:

Proton: Composed of two up quarks (each with a charge of +2/3e) and one down quark (with a charge of -1/3e), resulting in a total electric charge of +e.3
Neutron: Composed of one up quark and two down quarks, resulting in a net electric charge of zero.13

Because of the nature of the strong force, quarks are permanently confined within these particles and cannot be isolated as single entities.24