What You Need To Know Before You See Ant-Man And The Wasp

She's hardly onscreen outside a brief in-costume flashback, but Janet van Dyne's presence looms large throughout the film. She's Hank Pym's wife, Hope van Dyne's mother, and the original Wasp. Her tragic sacrifice is what leads to the rift between Hope and Hank, and it's only repaired when Hank tells Hope the truth of how her mother apparently died, trapped in the Quantum Realm.

Janet's death occurs when she and Hank are on a mission as Ant-Man and the Wasp. They're out to disarm a nuclear warhead but find that they aren't small enough to get inside the bomb to disarm it. Janet heroically sacrifices herself to stop the bomb, smashing her atomic regulator and shrinking down to a sub-atomic size. It allows her to disarm the bomb but also casts her into the Quantum Realm, effectively dooming her. 

Again, however, the end of Ant-Man proves that it's possible for someone to go to the Quantum Realm, survive, and then be brought back. This is why Hank is so fascinated with Scott's survival — it means there's hope that Janet could still be alive. Considering that the character is on the poster, it probably isn't much of a spoiler to say that that hope isn't futile. We'll be seeing more of Janet — and probably more of the Quantum Realm — as she'll be played by Michelle Pfeiffer in Ant-Man and the Wasp.