Stan Lee and Jack Kirby had created all sorts of superheroes for Marvel Comics. They had a team who had an accident in space and got super powers, they had a guy who was too close to a nuclear explosion and turned green, a dork who got bitten by a spider and suddenly got strange powers, the list goes on and on.
But in 1963, Lee and Kirby thought of an easier way to explain all the super powers some of their characters had: they were born with them.

Marvel Comics published the first issue of X-Men in 1963. The team, which consisted of Cyclops (Scott Summers), Marvel Girl (Jean Grey), Iceman (Bobby Drake), Angel (Warren Worthington III) and the Beast (Hank McCoy), was led by professor Charles Xavier, and fought the evil Magneto in the first issue. They all were so-called mutants, humans who were born with a special ability. This special ability usually was dormant until the person reached puberty, then the gift (or curse) would become visible.

Unfortunately for Xavier and his team, the comic got cancelled at issue 66 because not enough copies were sold each month. Instead, Marvel Comics started reprinting the X-Men's adventures in issue 67. While the X-Men comicbook was reprinting stories, the X-Men occasionally showed up in other comics.

That was until 1975, when Giant-Size X-Men #1 was published. The issue was written by Len Wein, with pencils by Dave Cockrum, and showed that the original team of X-Men was captured by the Living Island Of Krakoa. The island summoned Professor Xavier to form a new team of mutants, so it could feed its hunger. The new team consisted of Nightcrawler (Kurt Wagner), Banshee (Sean Cassidy), Sunfire (Shiro Yoshida), Wolverine (Logan), Storm (Ororo Munroe), Thunderbird (John Proudstar) and Colossus (Piotr Rasputin). They succeeded in rescuing the original X-Men. Giant-Size X-Men lasted only one issue, but it set the stage for new stories.

Chris Claremont restarted the X-Men comic with issue 94, which was the beginning of his 16 year run as writer. Over the years, he made the X-Men go through a lot of line-up changes. Some mutants joined, others left, even a few died. Claremont was responsible for classic stories like the Dark Phoenix saga, Days Of Future Past, the Brood saga, and many others.

With issue 114, the title officially changed to Uncanny X-Men. Uncanny X-Men would have quite a few spin-offs. The first one would be the New Mutants, which would later be turned into X-Force It had a different team of X-Men, not lead by Xavier. After a while, the two titles were still not enough to satisfy the readers, so a third title, X-Factor was launched. The X-Factor team consisted of the original team of X-Men: Cyclops, Beast, Angel, Iceman and Jean Grey.

Over the years, lots of X-Men titles have come and gone. Wolverine and Cable still have their own comic, but Gambit and Bishop apparently didn't sell well enough so their titles were cancelled. In 1991, X-Men was started by Claremont and Jim Lee. This was the second title to feature the team that was known as the X-Men, since Uncanny X-Men was also still published every month. Unfortunately, both Claremont and Lee would leave the title after only a few issues.

The X-Men still remain the most popular comics every month, and it's still Marvel's biggest moneymaker. Currently there are about 10 X-Men comics published each month, of which 6 are ongoing series.