  When string/M-theory is compactified to lower dimensions, the U-duality
symmetry predicts so-called exotic branes whose higher dimensional origin
cannot be explained by the standard string/M-theory branes. We argue that
exotic branes can be understood in higher dimensions as non-geometric
backgrounds or U-folds, and that they are important for the physics of systems
which originally contain no exotic charges, since the supertube effect
generically produces such exotic charges. We discuss the implications of exotic
backgrounds for black hole microstate (non-)geometries.
