Joss Whedon has called his Avengers to assemble, and the cast of Age of Ultron have obliged.

'Avengers 2' Robert Downey Jr Posts Behind-The-Scenes PHOTO From 'Age Of Ultron', What Is Iron Man Up To?

The Marvel film has been shooting for over a month now, but April 23 was the first day that Iron Man (Robert Downey Jr.), Captain America (Chris Evans), Hawkeye (Jeremy Renner), Hulk (Mark Ruffalo), Black Widow (Scarlett Johansson), and Thor (Chris Hemsworth) were all at Shepperton Studios together.

"Today was the first day of shooting "Age Of Ultron" when all of the Avengers we reassembled! Awesome sight!" tweeted Ruffalo in between his Earth Day messages.

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Although Marvel Studios is known for being extremely strict when it comes to keeping their films tightly under wraps, Ruffalo and Downey have posted a few set photos online. The comic book studio need not worry, however, since it is nigh impossible to glean any spoilers from the duo's snaps (see above).

With the heroes of 2012's The Avengers all filming together for the first time in years, writer/director Whedon had a few over-excited actors on his hands.

"Our first day on set had been a little giddy," Ruffalo confessed to his followers.

Fans can find out just what Ruffalo and Co. have been working on when The Avengers: Age of Ultron hits theaters on May 1, 2015.