Avengers Age Of Ultron: Mark Ruffalo Shares More Behind-The-Scenes Photos

filming is underway, and Mark Ruffalo has been keeping fans up-to-date by sharing some behind-the-scenes photo via social media. A couple days ago, Ruffalo shared a photo of Paula Price working some magic in the make-up department. Ruffalo wrote, "Make up. Age Of Avengers. Paula Price saves actor from himself. Magically makes grey disappear."

And yesterday, Ruffalo shared a photo of himself wearing a rather unusual mask. Ruffalo wrote, "Can you guess what this is?" We're guessing that it's a motion capture mask for the Hulk's facial expressions in Avengers: Age of Ultron.

is set to be released in movie theaters on May 1, 2015.