Nuclear physics is the field of physics that studies the constituents and interactions of atomic nuclei. Through research, nuclear physicists are leading us on a journey of discovery into the nucleus of the atom - the very heart of matter. The goal is a roadmap of matter that will help unlock the secrets of how the universe is put together. Nuclear physics research is focused on understanding the matter composed of quarks and gluons, which makes up 99% of the mass of the universe. Most of this matter is found at the core of atoms, the same atoms that comprise all we see around us (including ourselves). Researchers seek to answer questions such as how the universe evolved just after the Big Bang from a super-hot plasma of quarks and gluons, how the different elements of the universe were formed, and how a nucleus is made up of individual protons and neutrons interacting with each other with the strongest force in Nature. The protons and neutrons themselves are the basic bound states of quarks in the universe; how these states are formed from quarks interacting with the gluonic field described by Quantum Chromodynamics is still only poorly understood, and under active study.