Let's break One Direction down to the basics for a minute: They're five British and Irish boys who have achieved worldwide fame through (at least, in part) wearing cool, color-coordinated outfits, having awesome hair and singing ultra-catchy pop songs. With a blink-and-you'll-miss-it rise to superstardom, Harry, Niall Liam, Louis and Zayn have quickly secured a position in the hearts, minds and iTunes libraries of teenagers across the globe.
But what exactly happened along the way that made them into such a mega-phenomenon? We've highlighted 10 crucial moments in 1D's evolution, from their first awkward solo auditions on "The X Factor" UK to playing in front of screaming sold-out crowds on their US tour. Click through the slideshow below for a video history of the band that's got that "One Thing."
How many of these One Direction moments do you remember? Which video is your favorite? Sound off in the comments below or tweet @HuffPostTeen!