The current understanding in particle physics is that quarks and leptons are the most fundamental particles, meaning they are not composed of smaller constituents. According to the Standard Model, which is the prevailing theory describing the elementary particles and their interactions, quarks are considered to be point-like particles with no internal structure.
However, it's important to note that our understanding of particle physics is still evolving, and there may be phenomena or particles yet to be discovered that could deepen our understanding of the fundamental nature of matter. The search for new particles and phenomena beyond the Standard Model is an active area of research in particle physics.
Various experiments, such as those conducted at the Large Hadron Collider (LHC), are dedicated to exploring high-energy collisions to probe the fundamental structure of matter. These experiments aim to discover new particles, understand their properties, and explore possible extensions to the Standard Model.
While no smaller constituents than quarks have been discovered to date, ongoing research and technological advancements may unveil new insights in the future. The quest for a deeper understanding of the fundamental building blocks of the universe is a fascinating and ongoing scientific endeavor.