The Avengers have assembled.

Cinematic behemoth Avengers: Age of Ultron is upon us, box office records at its feet. It's the culmination of seven years of Marvel movies, a risky cinematic strategy, and, actually, a bit of misfortune.

Before the Avengers were the Avengers, they were Marvel 's JV superhero team. They weren't as cool as the X-Men, and they didn't have the tradition of the Fantastic Four. And there was a point where they weren't worthy enough to be mentioned in the same breath as Superman or Batman.

The Avengers are, in the greatest sense, a comeback story — a story no one at Marvel could have dreamed of writing.

Who are the Avengers?

When people talk about the Avengers now, they're most likely referring to the supergroup portrayed in Marvel's 2012 film The Avengers — which consists of Iron Man/Tony Stark (Robert Downey, Jr.), Black Widow/Natasha Romanoff (Scarlett Johansson), the Hulk/Bruce Banner (Mark Ruffalo), Thor (Chris Hemsworth), Hawkeye/Clint Barton (Jeremy Renner), and Captain America/Steve Rogers (Chris Evans).

The breakdown of the team is as follows:

Iron Man (guy in an armored suit): Smartass, very rich genius who has a powerful suit that allows him to fly and perform amazing feats in battle.

Thor (guy with hammer): Demi-god, ostensibly rich, not a genius but can control lightning.

Hawkeye (guy with bow and arrow): Semi-smartass master assassin who is only valuable to the team so long as he has his arrows.

Black Widow (woman): Smartass master assassin who doesn't need a bow and arrow to be valuable to the team.

Hulk (gigantic green guy): Not a fan of many syllables, but very, very strong.

Captain America (guy with shield, dressed like the American flag): Earnest super-soldier, usually the butt of the team's smartass jokes. Carries a large, incredibly strong shield.

The Avengers, according to Box Office Mojo, made $623,357,910 domestically and $1.5 billion worldwide. Its $207 million opening weekend is still the highest of all time. A megaton of people saw that movie, and it's become a major pop culture influence.

The film has also changed the movie business. Movies like Iron Man and Captain America fed into the plot of The Avengers, and subsequent movies like Captain America: Winter Solider were affected by the events of the movie. A connected universe of different films was unprecedented when Marvel did it, and now companies like DC and Warner Bros. are following suit.

These movies are based on adventures and characters in Marvel's Avengers comic books. But the movies haven't always been a straight translation. For example, characters like Black Widow, Captain America, and Hawkeye weren't part of Jack Kirby and Stan Lee's squad in Avengers No. 1 (1963):

The original roster featured the Hulk, Iron Man (looking much different than he does today), the Wasp, Ant-Man, and Thor.

They were heroes with disparate personalities. Thor was a majestic force, constantly using words like "scourge" and "incantations" mid-fight. Ant-Man and the Wasp, a romantic pair, were the slapstick comedic relief; she was always talking about her crushes on other superheroes, and he was always nagging her to snap out of it. Iron Man was an eccentric, egotistical playboy:

Kirby and Lee's first Avengers also delved into the theme of the Hulk being an unstoppable and dangerous force who wasn't in control of his own power. The first story is wrapped around the threat of the Hulk and how he might endanger humanity with his strength, even though he doesn't mean to:

But what's key here isn't actually the Avengers, but the inclusion of the Fantastic Four. When Avengers No. 1 debuted, the Fantastic Four were Marvel's crown jewel — the comic book had saved Marvel from a death spiral and was wildly popular. Lee and Kirby undoubtedly wanted to capture that same success.

The F4 were as much celebrities as they were heroes. So in Avengers No. 1, we see the F4 preoccupied with their own trials, but not before delegating some of their responsibilities to another group of heroes:

This handoff is an implicit seal of approval from the F4. If they trust this group of heroes, everyone else should, too. It also sets up the Avengers to follow the same superhero model as the F4 — they're not really mysterious or distrusted (the way the X-Men or Spider-Man are). Even though their roster has expanded over time, the Avengers will always be heroes you can trust, and they're here to save us all.

The F4-Avengers connection also established that all of these characters exist in the same world. Everything they do in their own comics affects Marvel's universe, and every single comic — Avengers, individual titles, Fantastic Four, X-Men, etc. — is part of one giant continuous narrative, just like the movies.

The Avengers were Marvel's JV squad

If we were to travel back in time 15 years, and Marvel had its choice of which heroes to make movies about, the Avengers would probably not be the company's first choice, nor its second, and maybe not even its third. The Avengers were the hand Marvel was dealt.

At the end of the '90s, Marvel was in a heap of financial trouble. The company was teetering on the verge of bankruptcy, and in order to survive, it took a scalpel to its comic book heroes and began selling off their film rights. Sony took Spider-Man, while Fox landed the X-Men and the Fantastic Four. Fox's get was huge, because the X-Men had dominated comic book sales throughout the '90s:

This helped the 2000 X-Men film achieve, according to Box Office Mojo, a domestic gross of $236,971,000 (adjusted for inflation). Sony's Spider-Man enjoyed the same kind of success. And Marvel, which was struggling, wanted that kind of financial windfall, but didn't have the same type of characters in its war chest that it had sold to Sony and Fox.

What it did have was the charismatic egomaniac Tony Stark and plenty of trust in Robert Downey Jr., who had beaten out Sam Rockwell, Timothy Olyphant, and Clive Owen for the role. Downey was arrested in 2001, and admitted to battling an addiction to drugs and alcohol. In the mid-2000s, he began making his come back in mainstream movies. While you could make an argument that his portrayal of Harry Lockhart in Kiss Kiss Bang Bang might be the best performance of his career (I would), there's no doubt that Iron Man has been his most successful.

Iron Man, as a character, did not have the same status as the X-Men, Spider-Man, Superman, or Batman. But the fit between Tony Stark and Downey was perfect.

Downey gave Stark the jerky, effortless moxie the character needed, and was a breath of fresh air compared with the very serious X-Men and Christopher Nolan's dark take on Batman. Iron Man was a fantastic hit, garnering $360 million (adjusted for inflation) in its domestic gross.

If the first Iron Man movie had bombed, we would have never had The Avengers. But more important, if Marvel had never signed away the rights to Spider-Man and the X-Men, it would have never been forced to try something different, to essentially give us a superhero story we didn't have. If Marvel still had the movie rights to X-Men, Spider-Man, and the Fantastic Four during its late-'90s financial woes, movies like Iron Man, Guardians of the Galaxy, or the upcoming Ant-Man wouldn't exist.

What is the main difference between the movies and the comic books?

The main difference between the Avengers stories you see on the silver screen and the comic books is the sheer size and diversity of the Avengers team. The Avengers, especially in recent years, have become a team that's welcomed progress and diversity.

You wouldn't know this from the movies.

Look at the Avengers in the photo above, and you'll notice it's dominated by white dudes (the Hulk in human form is a straight, white dude) and lacking when it comes to women and people of color. The addition of Scarlet Witch (Elizabeth Olsen) and Quicksilver (Aaron Taylor-Johnson) in Avengers: Age of Ultron makes the team even whiter.

A lack of diversity isn't as big a problem for the Avengers in the comic books. In recent years, Marvel has made a series of moves to include and spotlight heroes of color as well as female superheroes.

This year, Marvel debuted the cover to its All-New All-Different Avengers comic book. That team will feature an African-American Captain America, a Pakistani-American Ms. Marvel, a female Thor, and Miles Morales, a black-Latino character, as Spider-Man:

These Avengers obviously look very different from the Avengers we see in Marvel's films. And as it happens, the films account for only a few of the characters who are part of the Avengers in the comics, where they're a huge squad composed of dozens of people and different strike forces spanning several comic titles (Mighty Avengers, Young Avengers, Secret Avengers, Uncanny Avengers, Avengers, New Avengers, etc.). If your familiarity with the team is limited to its big-screen presence, you've only sampled a small slice of the gigantic Avengers universe.

Indeed, the movies are missing the space heroics and cosmic adventures of Captain Marvel, the trials and tribulations of She-Hulk, the hip and progressive Young Avengers, and the street-level fights that Luke Cage, Monica Rambeau, and the rest of the Mighty Avengers waged in the "Infinity" arc. There are also deeply personal stories like Vision's struggle with love and humanity, Black Panther's wedding and divorce, Carol Danvers and Tony Stark's struggle with addiction, and Scarlet Witch's tragic life, which are integral to their characters but rarely touched upon on screen (though this could change). And Hawkeye is a much more dynamic character in the comic books.

Finally, because comic books aren't subject to the same rights battles as the films, characters like Beast, Spider-Man, and Wolverine are becoming Avengers, while the Avengers are crossing over with the X-Men and the Fantastic Four.

Granted, the entirety of such an expansive universe would be impossible to portray on film. The common refrain from reviews of Avengers: Age of Ultron is that the movie can feel too crowded at times — and that's with just a fraction of the Avengers.

Why Ultron is crucial to the Avengers

Ultron is crucial to the Avengers' story because he represents pure evil.

For a long time, evil was typically represented in comic books by a villain with dreams of amassing a ton of wealth. He or she would rob a bank, get caught, and that would be the end of it. That didn't happen with Ultron.

Technically, the character first appears in Avengers No. 54 — written by Roy Thomas and illustrated by John Buscema in 1968 — but Ultron's debut isn't a true appearance, per se. In disguise, Ultron goes by the name Crimson Cowl and is, yes, draped in a crimson (pink) cowl.

Readers soon learn the Cowl has assembled a group of villains who want to take down the Avengers. Ultron wants to capture the Avengers, stick them in a hydrogen bomb, and blow it up over Manhattan:

In writing a story with such high stakes, Thomas wasn't just setting the form of one of the greatest Avengers villains in history — he was also changing the characterization of evil. The move helped usher in a different, darker way to tell stories.

Thomas, an English teacher in Missouri before his Marvel years, was an avid fan of comic books before joining Marvel, carefully positioned Ultron as a leader and ultimately demoting the Avengers' established group of foes, the "Masters of Evil" — a ragtag group of silly super villains like the Klaw and Whirlwind— by making them Ultron's puppets:

In with the new evil, out with the old.

Thomas's work on Ultron reflects the fears of the Cold War era. Joss Whedon has tweaked that in Age of Ultron, making Ultron embody the fears of AI and the singularity rather than a hydrogen bomb. But Ultron's nihilistic heart and mission remain the same.

The future of the Avengers

Avengers: Age of Ultron is already a hit, and Marvel has lined up sequels and Avengers tie-ins through 2019. So the next question is, "What kind of stories will Marvel choose to tell next?"

The studio has yet to showcase a female character or a nonwhite character in its movies. That's why there's a lot of attention on its upcoming Black Panther and Captain Marvel films — both characters are A-list Avengers in the comic books, and both have a rich history for Marvel to drawn on.

And Marvel, as it did with Iron Man, will have to figure out how to make these characters and their stories stand out if it wants to avoid the oncoming tsunami of superhero fatigue. In the next few years, Marvel will have to contend with Fox's X-Men: Apocalypse, Warner Bros.' Batman v. Superman, and a bevy of other films in its own hopper.

In addition to Black Panther and Captain Marvel, it will also be bringing Benedict Cumberbatch's Dr. Strange, Paul Rudd's Ant-Man, and Spider-Man into its fold. If Age of Ultron feels crowded with the addition of two characters, what will we be looking at come 2019, when the second half of Avengers: Infinity War hits theaters?

Even though Infinity War is the last Avengers movie on Marvel's schedule, that's only temporary. There's a deep well full of stories and characters that the company has yet to tap into. And there are plenty of stories involving characters already in the mix that Marvel hasn't even touched. If there's one thing Marvel and the Avengers have taught us, it's that this franchise will never die.