The holy grail of physicists has been to develop a “theory of everything,” a theory that would combine general relativity and quantum mechanics into one. Perhaps the most promising current idea for such a theory is called superstring theory. In it, vibrating strings, not point-like particles, are the fundamental constituents.
The different resonances of the strings create the different particles we see.
Each string is unimaginably small, about 1020, or 100 billion billion times smaller than a proton, and can vibrate only in a space-time consisting of 10 dimensions. Physicists and cosmologists will have to wait to see whether superstring theory ends up being the theory of everything—its predictions have to be verified, after all—or just another beautiful theory that falls by the wayside. But at least they have found a theory that seems worth pursuing.