James McAvoy
and Michael Fassbender play Professor Xavier and Magneto, respectively, in this June's 'X-Men: First Class,' (in theaters June 3) which will show the early stages of what would become a decades-long, and really quite complicated, relationship.

While it's too soon to know exactly how they meet in the movies, it seems clear that they find each other at the best possible moment: before mutants become a growing concern and an object of fear for humans. The central conflict that develops between the two men after that moment is their disagreement over exactly how to handle this new human-mutant relationship. Xavier, ever the peacemaker, thinks it vital to show humans that mutants are not a threat. Magneto thinks otherwise. He believes that he was born better than humans and has little reason to kowtow to what he sees as their tyranny.

We'll have to wait until 'X-Men: First Class' hits theaters to get the full details, but that's OK -- Xavier and Magneto have an well-fleshed-out history in comics already, and Moviefone will get you up to speed.

*The important thing to understand about superheroes like Professor X and Magneto is that while they've been around for decades, their actions have generally taken place in something resembling the present day. This leads to a few pretty amazing plot holes. Just relax and roll with it. The specific dates don't matter half as much as the relationships do. For example, if a character should be 60 years old but is clearly drawn in her late 20s, don't stress over it.

Young Xavier and Magneto: Best Buds
After graduating from Harvard at 16 and spending a few years at Oxford, Charles Xavier was drafted into the Korean War. He specialized in rescue missions rather than combat, perhaps due to his anti-fighting nature. After the war, he wandered around the world, getting into various misadventures that laid the seeds for the X-Men. While visiting a clinic in Israel intended for Holocaust victims, he met Erik Lehnsherr, who would later become known as Magneto.

This was before anyone even knew mutants existed, and both Xavier and Lehnsherr's powers were kept secret. Eventually, however, circumstances forced the two men to reveal their powers to each other, and they struck up an easy friendship. They enjoyed chess and debate, particularly on the subject of mutant rights. They could tell that mutants were going to be an important social and political issue in the future but differed on how to approach that issue.

Lehnsherr, due to his brutal experience in a World War II concentration camp, wanted to protect mutantkind from the predations of baseline humans.

Having seen the absolute worst that humanity has to offer, Lehnsherr refused to let that happen to his kind. He wanted mutants to emerge without needing to hide their powers or be subordinate to humans.

Xavier, on the other hand, took a more integrationist stance. He thought that mutants coming out slowly and obeying the laws of man was the best idea, hopefully to avoid any combat or strife.

Super-Powered Xavier and Magneto: Rival Teams
Despite their shared interest in supporting mutantkind, the two differed on mutant-human issues so drastically that they never managed to reconcile. After parting ways, they met years later as Magneto of the Brotherhood of Evil Mutants (yes, really) and Professor Xavier of the X-Men. By this point, Xavier's aversion to fighting had eroded somewhat, as the X-Men were (and are still) essentially a paramilitary mutant strike force. Magneto's protective stance, on the other hand, had evolved into pure terrorism, rather than anything pure of heart.

Their rivalry lasted years and transformed into several new configurations. At certain points, Magneto reformed and joined the X-Men, serving as a valuable and wise mentor to a new generation of mutants. Sometimes they had a working truce, while Magneto and Xavier sought space from each other and their near-constant battles. Their conflict suddenly reached an end when Xavier, in a moment of desperation, wiped Magneto's mind clean, leaving him amnesiac and catatonic.

This is comic books, though, and no one ever stays dead. It turned out that the act of wiping Magneto's mind traumatized Xavier, which soon gave birth to Onslaught, an evil combination of Magneto and Xavier. It took the combined might of the entire Marvel Universe, including Captain America, Iron Man, Thor and many others, to take Onslaught down.

Still later, Magneto finally realized his dream of becoming a protector of mutants once he became the leader of a mutant-led country. This soon ended, however, and after some trials and tribulations, Magneto rejoined the X-Men.

Veteran Xavier and Magneto: Odd Couple Roommates
Nowadays, Magneto and Xavier are not quite buddy-buddy, but they still manage to coexist on the same team. Xavier has retreated into more of an advisory role, while Magneto continues to go on combat missions. Very little attention has been paid to their current relationship, but it's fair to assume that that relationship is due for some upheaval fairly soon.

Their history in comics is long and layered, but if you get a chance to dig deeper, give it a try. For the foreseeable future, though, 'X-Men: First Class' is the easiest place to get your fill of Magneto and Xavier having deep conversations.