The strong force (also known as the strong nuclear force) is one of the four fundamental forces of nature. Strong force interactions are mediated fundamentally by the gluon. The strong force is responsible for binding quarks into mesons and baryons. The strong force is also responsible for binding protons and neutrons together in the nuclei of atom, overcoming the electrostatic repulsion of the protons. However, in this case the strong force is mediated by mesons.