







As he tells it, Stan Lee, a World War II veteran of the Army Signal Corps, was tired of comic books in 1961. He'd always considered comics a temporary gig but by that point had worked in the medium for 20 years, starting even before his military service.



He was burned out and ready to quit.



His wife Joan told him to stick with it a little longer — but to write a comic he wanted to write. A talk with his publisher about National Comics' "Justice League of America," a top-selling book featuring a team of superheroes, sealed the deal: He would write a superhero team book.



The Fantastic Four — and the Marvel Universe — were born.



The universe expanded quickly: Hulk, Thor, Spider-Man, Ant-Man and Wasp, Iron Man and the X-Men led a weird and wild pantheon of heroes and villains into American pop culture.





In partnership with artists Jack Kirby and Steve Ditko, among others, Lee created a vibrant two-dimensional world with modern sensibilities: Flawed heroes who argued and fought with each other, and who often found that having powers or a secret identity could prove to be a negative.

More than half a century later, that universe is virtually exploding, as the Marvel lineup has made the leap to the big screen for one blockbuster after another, each raking in billions and keeping fans hungry for more.

The secret, as Lee and his merry band discovered decades ago, is in the intricate way that the Marvel characters and their individual back stories are woven together, and constantly play off each other. For example, way back in the day, in the very first issue of his own comic, Spider-Man tries to join the Fantastic Four — but gives up when he finds out they don't pay. Similarly, in a nod to rival publisher DC's established Justice League, Lee and Kirby assembled a clutch of characters into a team called The Avengers.

Five decades later, that interconnectedness remains the hallmark not only of the endlessly churning Marvel comics universe, but its big-screen counterpart as well, with cosmic-scale events from one comic/film routinely rippling into other comics/films.

The opening salvo in the leap from page to screen was the blockbuster 2008 film "Iron Man." Comics fans flocked to it in droves, of course. But what really made their jaws drop was a scene near the end, when Nick Fury, head of the agency known as S.H.I.E.L.D. — Strategic Homeland Intervention, Enforcement and Logistics Division — showed up at Tony Stark's house to chat about the "Avengers Initiative."

That's when longtime fans began to realize they were in for a wild ride. Today, it's reached the point where you can hardly keep it all straight without a scorecard.

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Herewith, our primer on how the numerous main threads are woven together.

Some assembly required

Fury and his top operative, Agent Phil Coulson, appear again in "Iron Man 2" (2010), and it

seems that the initiative is already on shaky ground: Fury's bosses don't trust the mercurial Stark.

Coulson gets called out of "Iron Man 2" and sent into "Thor" (2011) to check out an anomaly that turns out to be the Thunder God's hammer, which had been dispatched from Asgard to Earth, along with a depowered Thor, by his father Odin as part of a lesson in humility for his arrogant and impetuous son.

At the same time as the title character in "The Incredible Hulk" (2008) is rampaging on the East Coast, Army Gen. Thaddeus "Thunderbolt" Ross uses a monster of his own, the Abomination, to try to take down the "jade giant," but fails. Ross later wants the Abomination to join the initiative, but is dissuaded by Stark.

Soon after, in the "The First Avenger" (2011), Captain America, long thought dead, is found in suspended animation, frozen in a chunk of ice near the North Pole.

Steve Rogers was the consummate 98-pound weakling. His attempts to join the Army during World War II, however, draw the attention of Dr. Abraham Erskine, lead scientist of Project Rebirth, tasked with creating enhanced "super soldiers."

Erskine admires Rogers' tenacity and sense of duty, and despite some misgivings from the top brass, Rogers is given the super soldier formula and doused with vita-rays, courtesy of Howard Stark, Tony's father, who later designs Cap's shield and costume.

The process works, but Erskine is assassinated. His death reverberates into the present, as attempts to recreate the formula underpin a number of big and small screen plot points: Bucky Barnes/Winter Soldier; Agent Peggy Carter and the last vial of Steve Rogers' blood; the Hulk and the Abomination; and Deathlok and the Centipede Serum — all due in no small part to the hunt for the super-soldier formula.

When Captain America is found, Fury finally has the hero around whom he can build a dream team.

The Tesseract

Loki, the evil brother in "Thor," vanishes at the end of the movie but returns at the beginning of "The Avengers" (2012), working with an unknown entity and wielding a scepter that, among other things, allows him to control the minds of others.

His goal is to take over the Earth and deliver to his partner the Tesseract, an ancient artifact that the Red Skull and his terrorist organization Hydra had used to power an array of super weapons during World War II.

In the mission that landed him in the ice, Cap stopped the Red Skull's master plan to wipe out America's major cities. The cube was briefly lost but recovered and delivered to S.H.I.E.L.D., where it sits in storage until Fury enlists astrophysicist Dr. Erik Selvig to help him develop weapons capable of handling the ever-growing threats facing the planet.

Loki, controlling Selvig's mind, uses the Tesseract to open a wormhole for the alien Chitauri to invade New York. The newly minted Avengers stop the invasion.

The Tesseract, along with Loki, is taken to Asgard — deemed too dangerous to remain on Earth. But Loki's failure also puts the world in the crosshairs of his mysterious partner: Thanos, an alien demigod obsessed with death and a set of powerful artifacts known as the Infinity Stones.

In plain sight

The Infinity Stones have been lurking in the movies almost the whole time. The Tesseract is the Space Stone, hidden on Earth by Odin eons before the Red Skull found it in "The First Avenger."

Loki's staff in "The Avengers" is powered by the Mind Stone, which later gives superpowers to the Maximoff twins, Scarlet Witch and Quicksilver.

In "Thor: The Dark World" (2013), Thor fights the "dark elf" Maliketh over control of the Aether, the Reality Stone. After the Thunder God triumphs, fellow Asgardians Sif and Volstagg deliver the Aether to the Collector, because "it is not wise to keep two Infinity Stones so close together."

In "Guardians of the Galaxy" (2014), the title characters learn the stones' history when they try to unload the Power Stone onto the Collector. The stones are six singularities that existed before the Big Bang, and after the birth of the universe, took on their current forms. They can be used only by very powerful beings. The point is proven when a slave tries to kill the Collector with the stone, destroying herself and much of the museum where it is housed.

The Guardians deliver the stone to the Nova Corps, an intergalactic police force, for safekeeping.

In "Avengers: Age of Ultron" (2015), Thor sees the stones during his mind-quest and helps bring to life the android Vision — born with the Mind Stone embedded in his forehead — before eventually returning to Asgard for his next movie.

Thanos has been watching all of it: Loki lost the Mind Stone and the Space Stone; his agent Ronan lost the Power Stone to the Guardians. Thanos has had enough,

and when he says, "Fine, I'll do it myself," and reveals an Infinity Gauntlet — a glove capable of housing the six gems — the table is set for the next two Avengers flicks, "Infinity War" I and II (due in 2018 and 2019, respectively).

Two stones remain unturned: Soul and Time, likely to be unveiled in "Dr. Strange" (2016) or in "Thor: Ragnarok" or "Guardians of the Galaxy 2" (both set for 2017).

The fall of S.H.I.E.L.D.

Though the Red Skull was apparently destroyed by the Tesseract, Hydra lived on in secret, slowly infiltrating S.H.I.E.L.D. Then in "Captain America: The Winter Soldier" (2014), the Soldier apparently assassinates Fury (no worries; he survives). Hydra runs rampant over S.H.I.E.L.D. until Cap, Black Widow and the Falcon stop its master plan. However, the damage is done: S.H.I.E.L.D. is reduced to a handful of agents, led by Coulson, who died in "The Avengers" but returned in the first episode of the ABC television series "Agents of S.H.I.E.L.D."

Throughout that show, Coulson's crew keeps battling Hydra, even as they discover the Inhumans, a splinter race of superpowered humans created by aliens in the distant past. Coulson calls in the Avengers to take out what appears to be the last Hydra stronghold, as well as repair S.H.I.E.L.D.'s last helicarrier, which is used during the evacuation of the Sokovian capital during Ultron's attack.

S.H.I.E.L.D. is on better footing, but Cap's upcoming "Civil War" (2016) will test it — as well as the tenuous bonds between the Avengers, especially Rogers and Tony, who, unlike their comic book counterparts, are not especially chummy. After defeating the genocidal robot Ultron, most of the original team split.

It's down to Cap and Black Widow to train new Avengers Scarlet Witch, Falcon, Vision and War Machine, but most of the original team is signed up, as is Ant-Man (whose movie opens July 17). Spider-Man, Dr. Strange, Captain Marvel and Black Panther, all of whom have movies coming soon, also may show up.

And that sets Marvel's movie slate through at least 2019, when "The Inhumans" will debut on the big screen.

What stories and characters will propel Marvel's screen endeavors into the next decade? If past heralds future, the threads are already woven into the

fabric.