To unite the seemingly incompatible worlds of the very large and the very small, physicists propose string theory, a model of the universe in which tiny strings vibrate in more than three dimensions. This Cribsheet covers the basics of string theory: what it says, why we think it might give us a unified theory of physics, and whether experiment supports it. In addition, we tell you how the strings are shaped and why string theory may not be the final “theory of everything.”