Nuclear fusion is a process in which two or more atomic nuclei come together to form a single, larger nucleus. This occurs when the attractive nuclear force overcomes the electrostatic repulsion between positively charged nuclei. During this process, a small amount of mass is converted into energy according to Einstein's famous equation E=mc^2. Nuclear fusion is what powers stars like our sun and it has the potential to provide clean, sustainable energy on Earth as well through experiments such as ITER (International Thermonuclear Experimental Reactor).