String Theory. Also known as the Theory of Everything. What is the stuff of all things? Physicists theorize that the entire universe and everything in it is made up of tiny strings of energy. Smaller than an atom. Smaller than a proton or electron. Smaller than a quark. Too small to see, some think this tiny string is a coil-like spring shape. Others think it is in the shape of a circle. I don't really know anything about physics, but I think – it's a circle.