Matter is made up of tiny particles called atoms, which themselves consist of protons, neutrons, and electrons. Protons and neutrons form the nucleus at the center of an atom, while electrons orbit around this nucleus

. At a deeper level, protons and neutrons are made of even smaller particles called quarks, and electrons belong to a class of elementary particles called leptons. These quarks and leptons are considered elementary because they are not made of smaller components

. Atoms combine to form molecules, and molecules combine to form the bulk matter we encounter daily. Different combinations of atoms create different elements and compounds, such as sodium chloride (common salt) or water, which have properties distinct from their constituent atoms

. In summary, matter is fundamentally composed of elementary particles (quarks and leptons) that form atoms, which in turn form molecules and the substances we observe in the physical world