The X-Men film series consists of superhero films based on the Marvel Comics superhero team of the same name. 20th Century Fox obtained the film rights to the characters in 1994, and after numerous drafts, Bryan Singer was hired to direct X-Men and its sequel, X2. Singer left potential third and fourth films to direct Superman Returns, leaving Brett Ratner to direct X-Men: The Last Stand. X-Men and X2 were met with positive reviews for their dark, realistic tone and subtexts dealing with discrimination and intolerance, while X-Men: The Last Stand was met with mixed reviews. After each film earned higher box-office grosses than its predecessor, three spin-off films were released. X-Men Origins: Wolverine, directed by Gavin Hood, focuses on Wolverine's origin story. X-Men: First Class, directed by Matthew Vaughn, focuses on the origins of Professor X and Magneto. The Wolverine, directed by James Mangold, focuses on Wolverine after the events of The Last Stand. X-Men Origins: Wolverine was met with negative reviews from the critics, while X-Men: First Class and The Wolverine were met with positive reviews. With six films released, the X-Men film series is the 15th highest-grossing film franchise ever, having grossed over $2 billion worldwide. It is set to continue with X-Men: Days of Future Past, a dual sequel to both X-Men: The Last Stand and X-Men: First Class, and a follow-up to The Wolverine, with Singer returning as director and X-Men: Apocalypse, a sequel to Days of Future Past.