WARNING: The following article contains spoilers for Ant-Man and the Wasp, in theaters now.
When Peyton Reed's Ant-Man came out in 2015, it delivered a heist-driven action comedy. However, it also proved to be a game-changer for the Marvel Cinematic Universe, introducing the concept of the multiverse via the Quantum Realm.
There, Janet van Dyne (Michelle Pfeiffer), the estranged wife of Hank Pym (Michael Douglas), remained stuck after going sub-atomic trying to stop a Soviet nuclear missile. Hank tried but couldn't engineer a solution to extract Janet because he was simply unable to locate her. Thankfully, Scott Lang (Paul Rudd) gave Hank and his daughter Hope (Evangeline Lilly) a sense of optimism, as he was able to visit the micro verse and return alive.
In Ant-Man and the Wasp, the search for Janet picks up steam, and we learn more about the inner-workings of this mysterious place.
One of the big things we learn is how the Quantum Realm's energy can be harnessed. Because Janet was marooned there for 30 years, she basically turned into a battery storing quantum energy. What's more, given her genius, she knows how to control it as it's become part of her essence.
This energy can be extracted straight from the source, too, as Hank and Hope show with their new invention, the Quantum Tunnel. This runway-like device probes for signatures and taps into the overall energy of the microverse, which is how they're finally able to lock onto Janet. And it's the reason Sonny Burch (Walton Goggin) is trying to steal the technology to sell on the black market.
It's a dangerous process, though, as we witness with the accident that created Ghost (Hannah John-Kamen), if the extraction is uncontrolled and humans are exposed to quantum energy outside of the realm, it leaves their molecules in a state of flux, which is why she is able to phase through material. Her body, her physical matter so to speak, is unstable, which is why she and Bill Foster (Laurence Fishburne) need Janet: To extract her energy, and use it to stabilize Ghost.