Iron Man 3 (2011) - Extremis Endoarmor Concepts

Early in the development of Iron Man 3, the Extremis serum was conceived of as a nanotech injection that would form an armored structure under the skin. Closer to what was in the original comic, it was conceptually a reflection of Iron Man's armor. The idea was to show some subtle bio-mechanical structure pushing up under the skin, and also allow the heat glow to backlight larger armor plates. While I much prefer the organic concept from the film thematically, this would have allowed some interesting design.