After three Marvel Studios films -- Captain America: The Winter Soldier, Captain America: Civil War and Avengers: Infinity War -- directors Joe and Anthony Russo have become masters of the tease. For proof, look no further than the release of a new behind-the-scenes photo that encourages fans to "look hard" for clues.

The moody black-and-white shot of Joe Russo sitting with his laptop on a relatively bare sound stage doesn't appear to reveal much, beyond stray equipment, and pieces of tape presumably marking where actors should look when facing CGI threats. But as one fan swiftly pointed out, there are four As in the photo, a nod to Avengers 4.

Look hard... pic.twitter.com/NxI8RFh4f6— Russo Brothers (@Russo_Brothers) September 19, 2018

The shapes of the letters are formed by the strategic placement of items around the set: at the camera on the far left, the easel near the center, the stepladder in the background, and the intersection of the duct work and backdrop. If there's more to the photo than that, undoubtedly eagle-eyed Marvel Cinematic Universe fans will ferret out the clues.

Four A's.
A4
AVENGERS 4

You can't hide anything from me. pic.twitter.com/MTk00CJRSH— Greywaren (@Jimmy2495) September 19, 2018

It's a clever tease that, in the end, doesn't actually reveal anything about Avengers 4. Instead, it feeds demand for any kind of morsel related to the Infinity War sequel without spoiling the plot. Considering how secretive the Russo brothers, and Marvel Studios executives, are about releasing details, there's no way they're unlikely to drop any breadcrumbs larger than this more than seven months away from the premiere.

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Directed by Joe and Anthony Russo, Avengers 4 stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Brie Larson, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Paul Bettany, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Karen Gillan, Evangeline Lilly and Josh Brolin. The film arrives May 3, 2019.