Frontman Billy Joe Armstrong told MTV News that 21st Century Breakdown had its creative spark drawn from bands such as The Who, Cheap Trick and The Ramones.
He said: "I love a lot of, like, British invasion. I love The Who and Cheap Trick and The Ramones. And it's like trying to take that power-pop or that pop-punk or whatever you want to call it, and stretching it into places that are further than we've ever gone."
The creative process also involved a pie chart tacked onto the wall at the band’s rehearsal space.
"We wrote sort of a pie graph thing, of different eras and genres on there, and we'd spin it, and it would say like, 'Death Metal,' '60s Garage Psychedelic' or whatever, and then we'd be forced to go in and write something with that...that's how it all started," drummer Tre Cool revealed.
Armstrong added: "I mean, technically, we were a slacker band back in the day...we didn't care about anything, but you keep evolving, you know? And I think we're capable of doing anything."