An up quark is a fundamental particle and one of the building blocks of matter. It is a type of quark, which are elementary particles that combine to form protons and neutrons, the components of atomic nuclei. Up quarks have a positive electric charge of +2/3 and are found in pairs with down quarks to create protons, or in combinations with other quarks to form different particles. Up quarks are part of the Standard Model of particle physics, which describes the fundamental forces and particles in the universe. They are classified as fermions, meaning they follow the Pauli exclusion principle, and they interact through the strong force, mediated by particles called gluons.