In the year 2000, superhero movies were at the precipice of a mainstream revolution, and leading that charge were the X-Men. But this was a new millennium and a new format. The tight, stretchy outfits worn by the team in their comics and iconic ’90s cartoon wouldn’t do. Instead, these X-Men donned black leather bodysuits. And yet, even that wasn’t cool enough for the most badass X-Man of them all.

When Hugh Jackman’s Wolverine first joins the X-Men and sees those bodysuits for himself, he says, “You actually go outside in these things?” Cyclops (James Marsden) replies, “Well, what would you prefer? Yellow spandex?”

With just seven words, X-Men sneakily shifted expectations for the entire superhero movie genre. Gone were the days of colorful skintight supersuits. Superheroes were cool. And in the year 2000, that meant they couldn’t wear spandex.

But how did spandex become so synonymous with superheroes in the first place? When did it fall out of favor? And, to ask an even simpler question, what even is spandex? The story of this miracle material and its surprising intersection with the world of comics reveals how a seemingly innocuous invention changed the course of pop culture history — in more ways than you realize.