At first, the notion of the Marvel Cinematic Universe was quaint, gestational idea—a fan-pleasing moment at the end of the first Iron Man, a batch of superhero movies (Hulk, Captain America, Thor) that linked into a fun "the gang's all here!" moment with the heroes vs. aliens spectacular that was The Avengers. If it hadn't worked, that would have been it. But it worked better, and made more money, than anyone predicted, and now the Marvel Cinematic Universe is a complicated, multi-platform organism that Captain America: The Winter Soldier is about to wreak a lot of havoc on when it's released Friday. Let's examine just what Marvel has set up, where Winter Soldier belongs in the grand scheme of things, and what happens next.

Phase One: Tentative Planning

I remember watching Iron Man with a couple friends in the theater on opening night, and silently freaking out at the end-credits scene where Samuel L. Jackson, as Nick Fury, told Tony Stark, "You've become part of a bigger universe, you just don't know it yet." My friends, not comic book readers, were baffled, and I tried to explain, but it seemed like a cute Easter egg for the hardcore fans more than anything else, as did Tony Stark dropping into The Incredible Hulk. It's only when Nick Fury and company traipsed around Iron Man 2, ruining its plot with larger world-building, that "Phase One" and the plan for an Avengers movie felt more real.

It all could have ended if Thor and Captain America: The First Avenger had bombed. In fact, neither was a mega-hit (Thor made $181 million domestic on a $150 million budget, and the first Cap made $176 million) but it was enough to keep things moving. During "Phase One," the links between movies amounted to little winks: Phil Coulson finding Thor's hammer at the end of Iron Man 2, Nick Fury poking at the Cosmic Cube at the end of Thor. Most were surprised when it all culminated in Joss Whedon's surprisingly sensible Avengers movie, which managed to tap into what makes the dynamics of a super-team interesting and found original ways to show off the same old action heroics.

Phase Two: Marvel's Hit Factory

When The Avengers blew the box office wide open, Marvel's little experiment became a set of forward-looking multi-year plans, plotted much in the way grand comic book arcs are (which unite various titles for major crossovers at least once a year). Last year's Iron Man 3 and Thor: The Dark World marked the beginning of "Phase Two," but were basically standalone films. Agents of S.H.I.E.L.D. launched on ABC in September but underwhelmed fans when it turned out to be a B-list action drama of little import to the larger world. Captain America: The Winter Soldier is the first "Phase Two" movie to really have an impact on the Marvel Universe at large (some spoilers follow).

At first, S.H.I.E.L.D. was basically just used as a catch-all term for the government, for the intelligence community, and the growing superhero infrastructure. But Whedon planted a seed of discontent in The Avengers, and the TV show expanded on the giant shadow agency's general creepiness. The Winter Soldier takes that to the logical conclusion and pits Captain America against evil elements within the agency. The result is the first Marvel movie to date that really messes with the established order of things and sets the scene for more experimentation going forward. While every other studio is still struggling to set up their own rival superhero series, Marvel is already cheerfully evolving its own.

The Winter Soldier mixes in existing characters like Cobie Smulders' Maria Hill and Scarlett Johansson's Black Widow with ease. In general, the whole "shared universe" is starting to feel less and less jarring. Iron Man 2 felt like it had crowbarred an advertisement for future films into an unrelated plot, whereas The Winter Soldier feels like its own movie. The jarring post-credit teaser (which relates to Avengers: Age of Ultron) is still present, but easier to take considering that it's out of the general flow of things.

Phase Three: What Happens Next

Age of Ultron is the culmination of Phase Two, and will be preceded only by Guardians of the Galaxy, a wacky cosmic adventure that probably won't have major implications for the other films immediately, but will seek to refocus the audience's perspective from a strictly earthbound setting to a galactic one. Guardians of the Galaxy looks like a ton of fun, so Age of Ultron may prove the tipping point. If it's a home run, Marvel's phase three (which will certainly include Captain America and Thor sequels, as well as Edgar Wright's Ant-Man and other unnamed projects) will have a clear path to billions. If things go sour, it could hurt Marvel's big plans, which include four street-level New York City hero shows on Netflix and possibly a Dr. Strange movie (he gets a cute name-check in The Winter Soldier).

The amount of planning going on here means we won't be rid of Marvel movies anytime soon. But the important thing Kevin Feige (who produces all the films and heads Marvel Studios) seems to understand is dialing back to avoid oversaturation. People might roll their eyes at Marvel's master plan, but having to watch a couple movies a year is hardly an overtaxing request, especially as they get consistently strong reviews.

What happens if Marvel keeps piling on? Will Agents of S.H.I.E.L.D. and its Netflix pals dilute the overall quality pool? Will Joss Whedon's admirable intent on producing a worthy sequel see him overshoot the mark? Robert Downey Jr. already called his script "very ambitious," which can be Hollywood code for "weird and complicated." And then, of course, there's Downey himself. He was the first Marvel actor to hint that he might not want to do this thing forever; Chris Evans has been making noise about retiring from acting too. In the comics, you can keep drawing everyone forever, but eventually, you're going to have to replace Iron Man. Will people keep caring once that happens?

The best news for Marvel right now is that it has gotten better and better at spinning all these plates. Thor: The Dark World and Captain America: The Winter Soldier are both rip-roaring fun that leave truly enticing story threads dangling for future films. The daunting challenge that Age of Ultron faces is in the smart hands of Joss Whedon. Agents of S.H.I.E.L.D. is starting to get a little better (it couldn't have gotten any worse). Marvel has no real reason to be nervous except for the old adage: all good things must come to an end.