Marvel Studios: Assembling A Universe is finally airing on ABC tonight, and it promises an all-access backstage pass into the Marvel cinematic universe. Included in the one hour documentary will be sneak peeks at Guardians of the Galaxy, Captain America: The Winter Soldier and Avengers: Age of Ultron, as well as the ABC TV series Marvel's Agents of S.H.I.E.L.D. A third and final clip has arrived, which features Robert Downey Jr. looking back at his role as Iron Man, which may very well come to a close with The Avengers 3. Go back in time to where it all began, as Tony Stark lifts off the pages of a popular comic book to win over the hearts of moviegoers everywhere.

Marvel Studios: Assembling A Universe airs March 18 on ABC.