  We review the structure of maximal $D=11$ and $D=10$ supergravities. Upon
dimensional reduction, these theories give rise to the unique maximal
supergravities in all lower spacetime dimensions $D<10$. In $D$ dimensions,
maximal supergravity exhibits the exceptional global symmetry group E$_{11-D}$,
part of which is realized as hidden symmetries and only manifest after proper
dualization of the fields. We also briefly review the reformulation of $D=11$
supergravity as an exceptional field theory which renders the appearance of
hidden symmetries manifest.
