Nuclear physics
Nuclear physics is the part of physics that studies the nucleus of the atom. Everything on the earth is made up of atoms; they are the smallest part of a chemical element that still has the properties of that specific element. When two or more atoms combine they create what we know as the molecule, which is the smallest part of a chemical compound which still has the properties of that specific compound. Understanding the structure of atoms is key in studies such as physics, chemistry, biology, etc.