Supergravity is a class of point-particle theories, developed in the 1970s, which attempted to unify general relativity and supersymmetry. It employed 11 dimensions – the conventional four of ordinary spacetime plus seven compactified dimensions, effectively rolled up into a higher-dimensional sphere. Although it fell from favor with the rise of string theories, it has recently resurfaced in a new guise known as M-theory, which is also 11-dimensional.