Bryan Singer has big plans for X-Men: Days of Future Past. The director who proved that superheroes can work on film with 2000's X-Men returns to the franchise with a sequel to 2011's X-Men: First Class that not only features alternate timelines but reintroduces characters from the original trilogy.

"It's epic," he told Empire. "I don't think people realize how big this movie's going to be. We get to bring both casts together."

Singer revealed he turned to other directors and films to help figure out the science behind the sequel's prominent time-travel elements. "We've cracked it in a way that it makes sense," he said. "I had a two-hour conversation with James Cameron about time travel, string theory, multiverses and all that. You have to create your rules and stick wtih them. That's why Terminator and Back To The Future work so well. And there are certain mechanisms in X-Men, certain powers, perceptions and characters, that make this possible."

Singer also addressed a question many fans have had about which films will be included in the continuity of Days of Future Past. "I’m taking into account every movie – I’m not just grabbing my first two movies and First Class and smashing them together," he said. "I’m taking into account the entire universe as it’s been laid out so far on the screen, and really respecting it and trying to work with that. People took things in various directions, so there’s some clean-up. But ultimately I’m not just ignoring them either."

X-Men: Days of Future Past is set to debut in theaters on July 18, 2014.