'Iron Man 3' is set to start filming in May and yet we've heard little about the movie's plot or possible villains. Until now, that is.

'Avengers' writer/director Joss Whedon recently said he'd like any sequel to that behemoth to go smaller and more personal, and 'Iron Man 3' writer/director Shane Black may be thinking along the same lines by taking the story right inside Tony Stark's (Robert Downey Jr.) body.

According to Latino Review, one aspect of the storyline for 'Iron Man 3' involves nanobots -- you know, those tiny little robots that can get up to all kinds of trickery if they're injected into a human being. For the comic book fans among us, that can only mean one thing for Tony...the creation of Extremis.

In the comics (most notably 'Invincible Iron Man' Vol. 4, #1 - #6), Stark is injected with the Extremis "virus" -- which is actually a nanotechnology that effects all kinds of radical changes to him. Most significantly, he can interface with his Iron Man suit directly through his brain, making him and Iron Man a cyborg of sorts with greatly enhanced powers.

The Iron Man armor in both movies so far has leaned heavily on the design of the Extremis armor, and there have been small hints (such as Tony's search for an antidote to the palladium poisoning in 'Iron Man 2') that we could be looking at an Extremis-based storyline for Downey's fourth adventure in the suit.

Apparently there's also a clue in 'The Avengers' -- a line uttered by Captain America (Chris Evans) -- that leads Tony down the Extremis path, which means that once again Marvel is neatly segueing from one movie to the next. And if Extremis is involved, could we also see the long- awaited appearance of the Mandarin? Or even -- for the hell of it -- Ultron?

These are the things that will keep geeks awake at night until 'Iron Man 3' hits screens on May 3rd. 2013.