Especially as the movie expands on the post-apocalyptic world by sending Tris, her boyfriend Four (Theo James) and their friends beyond Chicago to the futuristic home of the Bureau of Genetic Welfare, run by the mysterious David (Jeff Daniels).

The cast of Divergent will reunite for the fourth film too

"It's a completely different organism," Woodley says of the Bureau. "It has its own political leaders. It's a full-blown running society. And I think when Tris and Four enter they're a little hesitant of it and also very keen on the luxuries that come with a world that's not war-torn. It's functioning and has access to things that they didn't have in Chicago."

She also found it interesting that the plot pushes Tris and Four in separate directions. "They're very much out of contact and not in communication with each other," she says. "And they both see different sides of who this David person is, and that creates distance between them."

Shooting the film required a lot of physicality, mainly lots of running plus one big stunt sequence. "The wall scene was really impressive," Woodley says, "because when we were filming, we were in fact scaling a real wall, but we were in some random large parking lot in Atlanta! So to see that translated into this giant landscape and environment, it put it in perspective in the dimensional world."

But it's the story's themes that she thinks make this franchise stand out. Along with the core issue of diversity ("It's important for everyone to be different and have different thoughts"), Woodley sees the saga as a cautionary tale about climate change. "Hopefully, the younger generations watching these movies are thinking about these problems," she says. "One can only hope! But you can do something as small as unplugging things and using small amounts of water, or you can stand up against pipelines and fossil fuel companies."

And despite her growing success, the Oscar-nominated actress refuses to play the fame game. "Some people crave celebrity," she says. "That's great for them, but that's so not me. Why would I change my lifestyle to the way other people react? I can still go anywhere. I just go out in normal clothes without makeup, and nobody notices."

Watch the trailer for Divergent Allegiant: