​Directing brothers ​Joe and Anthony Russo are not only the godfathers of the Marvel Cinematic Universe, but also some of the most socially engaging auteurs in Hollywood today. They have used their shared Twitter account in the past to promote their films, highlight the work of those behind the cameras, and to tease their upcoming projects.

Their most recent post is an obscure tease of, presumably, the set of their as-yet untitled 'Avengers 4.' The black and white image shows Joe sitting with his back to the camera on a largely empty set littered with backgrounds, stands, easels, and other paraphernalia. Captioned "Look hard...," the post invites viewers to search for a hidden clue about the highly-anticipated film.

Fans online who have pored over the photo have largely come to the conclusion that there is a hidden message in the picture, as many of the set pieces resemble letters. One fan pointed out how there were four 'A's hidden in the photo, signifying '​Avengers 4.' Another found a pattern which read 'endgame,' and posited it might be the title for the film.

Still, more fans believe the numerous 'X's in the shot indicates that Disney's recent acquisition of Fox has allowed the Russo brothers to bring the X-Men into the MCU. Others think the clue is on one of the obscured storyboard posters Joe is apparently examining. As of now, it is unclear just what the Russos are hinting at.