With the huge success of movies based on comic books, it’s hard to imagine a time when comics weren’t regarded as mainstream entertainment. Indeed, those old enough to have been collecting comics over the past few decades likely remember a time when admitting their love for comic books was tantamount to wearing the scarlet letters “N-E-R-D” seared on their foreheads. So what caused this change in perception regarding the American comic book?Comic books have been popular since being introduced in 1934. In the Golden Age of Comic Books it wasn’t uncommon for a single issue of Captain Marvel to sell over a million copies per issue. But these comic books were geared toward (and consumed by) kids. Contrast that to Japanese manga, which has long been considered an adult-oriented art form. Those creators often tell their stories with enough graphic impact to make Wolverine blush.Beginning in 1961, Stan Lee (along with venerable co-creators Jack Kirby and Steve Ditko among others) ushered in the Marvel Age of Comics and upended the comic book world by refusing to cater solely to children. Lee’s idea of having fantasy characters grappling with real-world problems added an extra layer of depth to the heroes and the stories. This formula of character development and reality-based conflicts is the standard approach for today’s creators of superhero comics. The Marvel Age matured during the 60s, and characters like Spider-Man were adopted by college students (who, as baby-boomers, would carry their love of comics into adulthood) and were regarded as anti-establishment in contrast to the more traditional and staid DC paragons like Superman. Marvel made news in the 70s by issuing books without the Comic Code Authority stamp and introducing minority characters as more than sidekicks.DC made up ground in the 80s, shaking up the comic book world with the introduction of two titles that would help comics gain greater respect: Alan Moore’s “Watchmen” and “The Dark Knight Returns” by Frank Miller. These books may be the most pivotal in terms of helping American comic books become viewed as a mainstream literature fit for adults. Christopher Nolan’s “Dark Knight” film franchise in particular owes a debt to Miller’s gritty, noir take on Batman.Today, DC is making headlines by rebooting their entire superhero universe. Superman will be younger and brasher, and his uniform will have a metallic look with the “S” shield altered. And while Kal-El is still decent, the red shorts are gone. Whether this radical reorganization of the DC Universe will succeed — and how it will impact comics — remains to be seen. But the fact that it’s fodder for water cooler talk by adults just shows how much the perception of the American comic book has changed.