What fundamental particle is responsible for making up protons and neutrons?

Protons and neutrons, which are the building blocks of atomic nuclei, are composed of even smaller particles known as quarks. Specifically, protons are made up of two up quarks and one down quark, while neutrons consist of one up quark and two down quarks. This fundamental composition is central to the structure of matter in the universe. Quarks interact via the strong force, which is mediated by particles called gluons. Understanding quarks is essential for comprehending the Standard Model of particle physics, which describes the fundamental forces and particles that make up the universe.

In contrast, electrons are a type of lepton and do not combine to form protons or neutrons; they exist in the electron cloud surrounding the nucleus. Photons are force carriers of electromagnetic radiation and do not have mass or contribute to the mass of atomic nuclei. Leptons, while an integral part of the Standard Model, do not account for the composition of protons and neutrons specifically. Thus, quarks are the correct fundamental particles that make up protons and neutrons.