According to our current understanding in particle physics, quarks are considered to be fundamental particles. Quarks are elementary particles that are the building blocks of protons and neutrons, which are collectively known as hadrons. They are not observed in isolation but are always found bound together in combinations called color-neutral composite particles.
Quarks come in six different types or flavors: up (u), down (d), charm (c), strange (s), top (t), and bottom (b). Each quark has an electric charge that is a fraction of the elementary unit of charge, and they also carry a property called "color charge" which relates to the strong nuclear force.
Quarks are governed by the laws of quantum chromodynamics (QCD), which is a part of the Standard Model of particle physics. QCD describes the strong nuclear force and how quarks interact through the exchange of particles called gluons.
Experimental evidence, such as high-energy collision experiments and deep inelastic scattering experiments, supports the notion that quarks are fundamental particles. However, it's worth noting that our understanding of fundamental particles is continually evolving as scientific research progresses. Future discoveries or breakthroughs may lead to revisions or expansions of our current understanding of quarks and other elementary particles.