Leptons are elementary particles, which means they are not made up of smaller components. They are considered fundamental particles in the Standard Model of particle physics, which is the current theory describing the fundamental particles and their interactions.
Leptons are believed to be point-like particles, meaning they have no known substructure or internal constituents. In other words, they are not composed of anything smaller or more fundamental. They are indivisible and do not appear to be made up of smaller particles.
There are six known types of leptons in the Standard Model: the electron, muon, tau, and their corresponding neutrinos. Each lepton has its antiparticle counterpart with opposite charge. For example, the antiparticle of the electron is called the positron.
Leptons interact through the fundamental forces of nature, such as the electromagnetic force and the weak nuclear force, and they do not experience the strong nuclear force that binds atomic nuclei together. Their interactions are described mathematically by quantum field theories, such as quantum electrodynamics (QED) and the electroweak theory.
While leptons are considered elementary particles in the Standard Model, it's important to note that our understanding of the fundamental nature of particles is always subject to revision as scientific knowledge advances. New discoveries or theoretical breakthroughs may lead to a deeper understanding of the underlying structure of leptons and other particles in the future.