The fundamental particles of the universe that physicists have identified—electrons, neutrinos, quarks and so on—are the "letters" of all matter. Just like their linguistic counterparts they appear to have no further internal substructure. String theory proclaims otherwise. According to string theory, if we could examine these particles with even greater precision—a precision many orders of magnitude beyond our present technological capacity—we would find that each is not pointlike but instead consists of a tiny, one-dimensional loop. Like an infinitely thin rubber band each particle contains a vibrating, oscillating, dancing filament that physicists have named a string.
This simple replacement of point-particle material constituents with strings attempts to resolve the incompatibility between quantum mechanics and general relativity which, as currently formulated, cannot both be right.