Quarks are, as far as we know, the smallest building blocks of matter. It takes 3 quarks to make up a proton or neutron. Nucleons , another name for protons and neutrons , are made up of quarks. One or more nucleons bound together form an atomic nucleus. A nucleon is the smallest object we know of that has internal structure.
Nuclear physicists study the internal stucture of nucleons as well as the structure of nuclei.
The nucleus sits at the center of an atom, and the number of protons in the nucleus determines which element the atom will be. The Atom consists of electrons bound to a nucleus by electrical forces. Because the electrical force is much weaker than the nuclear force, an atom is almost 100,000 times larger than the nucleus. Cells are what every living thing is made of. A cell is held together by chemical forces between molecules, which are collections of atoms.