The question of whether there is an ultimate end or a fundamental building block of the universe is a profound and ongoing area of scientific inquiry and philosophical debate. Our current understanding, based on the Standard Model of particle physics, suggests that quarks and leptons (such as electrons) are indeed fundamental particles. They are considered elementary, meaning they have no known substructure.
According to our current understanding, quarks combine to form protons and neutrons, which are the building blocks of atomic nuclei. Electrons surround the nucleus and are fundamental particles themselves. The interactions among these particles give rise to the macroscopic world we observe.
However, it's important to note that scientific knowledge is constantly evolving. While quarks and leptons are considered elementary particles within the framework of the Standard Model, it is possible that future discoveries or advancements in our understanding could reveal a deeper level of substructure or new fundamental entities.
In theoretical physics, various models and hypotheses, such as string theory, propose the existence of additional fundamental particles or entities that could provide a more comprehensive explanation of the universe. However, these ideas are still under active investigation, and experimental evidence is needed to validate or disprove them.
Ultimately, the question of whether there is an infinite regress or a fundamental end to the structure of the universe is a profound philosophical and scientific question that remains open for exploration and further understanding.