Marvel's 2006 comic storyline Civil War is one of the most interesting and well known series in recent memory. The story saw unlikely rivalries and alliances as heroes fought heroes and villains fought villains. Its popularity made it a natural choice to expand the Marvel Cinematic Universe.

"Captain America: Civil War" will hit theatres on May 6, 2016, and it will feature the titular hero going toe-to-toe against Robert Downey Jr.'s Iron Man. Fans know that filming will begin on April 1, and now they also know the official plot synopsis.

"Following the events of Age of Ultron, the collective governments of the world pass an act designed to regulate all superhuman activity. This polarizes opinion amongst the Avengers, causing two factions to side with Iron Man or Captain America, which causes an epic battle between former allies."

Daniel Bruhl ("Inglorious Basterds," "Rush") has been cast as villain Baron Zemo for the film. Additionally, "Civil War" will likely see the debuts of Black Panther and Spider-Man in the MCU.