Four years ago, One Direction were just five guys auditioning for the U.K.'s "X Factor." Today, they're one of the biggest pop acts on the planet.

On July 23, 2010, Simon Cowell pulled Liam, Louis, Niall, Harry and Zayn together, forming what Harry called "One Direction." And although they didn't win the show (they placed third), they signed a record deal soon after, and the rest is blissful, handsome history!

It's been a while since we've met the boys. Four years is enough time for you to go to college and get a degree. Four years is enough time to live out the lifespan of your MacBook. Four years is enough time to grow from a boy to a man.

I know I'm being dramatic, but this warrants it. Today is a special day for Directioners worldwide and for the band itself, which is why Niall Horan, Liam Payne and Harry Styles got sentimental this morning on Twitter.

"I can honestly say, thank you all so much, every one of you, from all over the world! Your support is absolutely incredible," Niall wrote, continuing, in what we can imagine him saying with his Irish accent, "What you have done for us baffles my mind ever day! really appreciate everything ! Thank you , love you! Let's have more fun now #4YearsOf1D."

If you're a Directioner, as I'm sure you are, all this is emotional. After all, when you analyze how far the band has come, it's pretty amazing.

Louis used to work as a waiter, Harry at a bakery. Now, they're currently on their third world tour, with another booked for 2015 with sold-out shows. They're also working on their fourth album (their previous three were all #1, selling 14-million copies worldwide altogether).

It's enough to make you weep.

Here are some of the best tributes to 1D I've seen on Twitter so far: