The first restriction on the geometry of a moduli space was found in 1979 by Bruno Zumino and published in the article Supersymmetry and Kähler Manifolds. He considered an N=1 theory in 4-dimensions with global supersymmetry. N=1 means that the fermionic components of the supersymmetry algebra can be assembled into a single Majorana supercharge. The only scalars in such a theory are the complex scalars of the chiral superfields. He found that the vacuum manifold of allowed vacuum expectation values for these scalars is not only complex but also a Kähler manifold.