When it comes to the fundamental laws of nature, we can break everything down into four forces that are at the core of everything in the Universe: The strong nuclear force: the force responsible for holding atomic nuclei and individual protons and neutrons together. The electromagnetic force: the force that attracts and repels charged particles, binds atoms together into molecules and life, and causes electric current, among other things. The weak nuclear force: the force responsible for some types of radioactive decay and the transmutation of heavy, unstable fundamental particles into lighter ones. And gravity: the force that bind the Earth, the Solar System and the stars and galaxies together.