The Elegant Universe

String theory is a developing branch of theoretical physics that combines quantum mechanics and general relativity into a quantum theory of gravity.[1] The strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces, too.
Since its birth as the dual resonance model which described the strongly interacting hadrons as strings, the term string theory has changed to include any of a group of related superstring theories which unite them. One shared property of all these theories is the holographic principle. String theory itself comes in many different formulations, each one with a different mathematical structure, and each best describing different physical circumstances. But the principles shared by these approaches, their mutual logical consistency, and the fact that some of them easily include the standard model of particle physics, has led many physicists to believe that the theory is the correct fundamental description of nature. In particular, string theory is the first candidate for the theory of everything, a way to describe all the known natural forces (gravitational, electromagnetic, weak and strong interactions) and matter (quarks and leptons) in a mathematically complete system.