It's no secret the Marvel Cinematic Universe is slowly building to an all out Captain America vs. Iron Man. This is why Captain America's third movie is called Civil War. And in this brand new Avengers: Age of Ultron clip, you can see the tension mounting.
This animosity has always existed – even in the very first Avengers.
But what's telling about the Age of Ultron clip up top is that the argument between Cap and Stark we see here isn't like the one in the first Avengers. This isn't just two hot-heads mouthing off. It's grounded in emotion. Things will, no doubt, only become more complicated for these two as things progress.
The clip itself is allegedly referencing the group's run-in with Elizabeth Olsen's Scarlet Witch, an encounter Steve Rogers says pulled them "apart like cotton candy." Not good. It looks like everyone has since retreated to lick their wounds.