Fan conventions, as any Trekkie can tell you, have grown enormously over the years and focus on myriad pop culture subjects and subcultures. These include anime, science fiction, horror and steampunk, to name a few.

Fans of comic books are perhaps the most fervent and flamboyant – many attendees dress up with great care and detail as their favorite character. Gatherings for devotees of superheroes, villains and lesser-known characters from the Marvel and DC Comics universe, among others, draw big crowds. The largest is Comic-Con, whose annual convention at the San Diego Convention Center starts today and runs through Sunday, July 12.

Comic-Con has counted 130,000 attendees at each of its conventions the past few years, and in fact it has outgrown the convention center (there were more than 700 sessions listed in the 2014 program). It now holds satellite events in area hotels and parks in San Diego.

Comic-Con and other comic book conventions focus on comics old and new – such as the upcoming reboot of the Archie series. But Comic-Con, largely because of its proximity to Hollywood, is also dominated by movies and TV shows and the attendant glitz (read: movie stars!). Some of the big deals this year at Comic-Con are the Warner Bros. presentation of Batman vs. Superman: Dawn of Justice, with Ben Affleck and Henry Cavill, and new details about X-Men: Apocalypse, still in production.

Comic Con and Other Comic Book ConventionsMany events, panels and screenings have little to do with comics, but who doesn’t want to get a jump on the final film installment of The Hunger Games, or see stars from Game of Thrones and Doctor Who? Quentin Tarantino himself will screen his new movie, The Hateful Eight.

Comic-Con gives the convention center’s exhibit hall, at more than 460,000 sq. ft., a workout. In addition to exhibitors, the program features hands-on workshops and educational and academic sessions; anime and film screenings (including a separate film festival); games; the Will Eisner Comic Industry Awards, the “Oscars” of the comics industry; a costume competition; an autograph area; an art show; and portfolio reviews, where major companies meet aspiring artists.

Other comic book conventions are scattered all over the country and around the world. The major ones include  New York Comic Con, to be held this year Oct. 8-11 at the Jacob Javits Center; Emerald City Comic Con, Stan Lee’s Comikaze Expo 2015 Oct. 30 – Nov. 1 held at the Los Angeles Convention Center , coming April 7-10 of next year at Washington State Convention Center; and WonderCon (presented by Comi-Con), coming March 25-27, 2016, at the Los Angeles Convention Center.