  In this review, we give a brief introduction on the aspects of some extra
dimension models and the five-dimensional thick brane models in extended
theories of gravity. First, we briefly introduce the Kaluza-Klein theory, the
domain wall model, the large extra dimension model, and the warped extra
dimension models. Then some thick brane solutions in extended theories of
gravity are reviewed. Finally, localization of bulk matter fields on thick
branes is discussed.
