Grand unification in extended supergravity

This paper reviews recent attempts to forge a connection between grand unified theories of elementary particle interactions, and extended supergravities. The spectra, multiplets, hidden symmetries, and dynamics of extended supergravity theories are reviewed. A scenario of the geological stratigraphy of elementary particles is pursued for the purposes of definiteness. It is determined that the bound state supermultiplet is too chiral, and that some way must be found to discard the unwanted helicity states. Extra helicity states, to ''eat'' the unwanted ones, and an infinite set of bound state supermultiplets are proposed. As the problem of the disposal of unwanted helicity states remains central in attempts to embed grand unification in extended supergravity using composite fields, more detailed dynamical studies are needed