in most of these theories gravity is not unified with the other interactions since they belong to different supermultiplets.

    -   However, *extended* ($N>1$) supergravities contain in the same supermultiplet of the graviton additional bosonic fields that may describe the other interactions. In this scheme all interactions would be described in a truly unified way.

        These extended supergravities can in general be obtained from compactification of simpler higher-dimensional supergravities. It was also discovered that many $N=1$ supergravities coupled to Yang-Mills fields could also be obtained in the same way, by a careful choice of compact manifold (i.e. Kaluza-Klein vacuum). This lead to a new brand of unified theories which could describe everything (*Theories of Everything*). The first of these is

9.  **Kaluza-Klein Supergravity [@Duff:1986hr; @Appelquist:1987nr]**

    It is a combination of the Kaluza-Klein theories with supersymmetry. Now, a Kaluza-Klein vacuum is (arbitrarily) chosen that breaks spontaneously part of the (super)symmetries of the “original” vacuum (Minkowski spacetime for Poincaré supergravities and anti-De Sitter spacetime for aDS supergravities). Now, the rule of the game, the *supersymmetric Kaluza-Klein Principle*, is

    > *Global (super)symmetries of the vacuum are local (super)symmetries of the compactified theory*.

    In general, the theories were based on compactifications of $N=1,d=11$ supergravity [@Cremmer:1978km], 