Since Einstein, physicists have been pursuing a single theory that would order all of the elementary particles in the universe and unify all the forces of nature. Such a theory would answer questions like: how did the universe begin?; what is the origin of time?; what is matter? In 1984 a theory - involving superstrings - burst upon the scientific world; a theory which, although seeming to defy the imagination, at the same time appeared to explain these physical phenomena. This book sets out to explain its development and meaning in a manner accessible to readers with no knowledge of mathematics.