The Quantum Realm was introduced in 2015's Ant-Man and the Wasp. Expect this strange new plane of reality to be very different to any of the other dimensions we've explored in the MCU to date.
The Quantum Realm was initially described as "a reality where all concepts of time and space become irrelevant as you shrink for all eternity." Hank Pym had previously believed that anyone - or, indeed anything - to enter the Quantum Realm would be destroyed; when Scott Lang successfully emerged from this dimension, he realized he was wrong. Pym has now dedicated himself to creating a new vehicle with which to explore the Quantum Realm.
Related: Why Ant-Man Could Be the Key To Defeating Thanos in Avengers 4
Speaking to Screen Rant during our visit to the Ant-Man and the Wasp set, executive producer Stephen Broussard insisted that the Quantum Realm will be a unique and unusual place - and nothing like the "black light, bioluminescent" Dark Dimension. He briefly showed us early concept art, but stressed that none of it was "completely accurate":
"It can’t be a black void, right like you had a little bit in the first film, so it’s gotta be landscape-y, but how do you make it still feel at scale? How do you make it feel microscopic with the camera treatments and with the relationship of the horizon and stuff like that? Figuring all that out has been a bit of a head trip, but it’s pretty cool. You know, it can’t just feel like -- I don’t know it’s not Lawrence of Arabia. It’s not a giant desert because that kind of -- it triggers scale cues in your head, but you still have to kind of feel that it would be scale appropriate if you’re down there and finding that balance between the small and the epic, I guess has kind of been the challenge."
The comments suggest the Quantum Realm left Marvel faced with some very different challenges. The fundamental issue was creating a sense of scale, a balance between "the small and the epic." We've had glimpses of the Quantum Realm in the Hank Pym's "pod" seems to be adapted from vehicles comic book readers have seen in the pages of Fantastic Four.
The Quantum Realm is expected to play an important role in the future of the MCU. It can be accessed both by science and by magic (Doctor Strange visited there when traveling across the dimensions in his solo film). Star Avengers 4.
That's only a theory, but one thing seems certain; Ant-Man and the Wasp's production team's design for the Quantum Realm is one Marvel will revisit in the future.
