Starting with their initial meeting at the 2017 Billboard Music Awards, we've rounded up everything we could find about Halsey and BTS.

A few years ago, then-rising pop star Halsey met K-pop’s biggest boy band, BTS -- and swiftly became one of its most vocal fans. Take a look at a famous friendship’s evolution (or, every time Halsey proved she's ARMY) below.

May 21, 2017 - A friendship is born

The start of it all. Halsey meets BTS at the 2017 Billboard Music Awards, where she told them their videos were "the coolest." The singer also gifts the group churros before they perform in front of an American audience for the first time.

ok i just met @BTS_twt and they are the coolest! -------- WOW — h (@halsey) May 21, 2017

Aug. 7, 2018 - Meet-up in South Korea

One day after Halsey performs in Seoul as part of her Hopeless Fountain Kingdom World Tour, the singer hangs out with the legendary boy band and posts pictures on Instagram to prove it.

"You know there was no way I’d come all the way to Seoul without seeing these guys," the 24-year-old singer writes in a (since-deleted) post. "Can’t wait to see them play Staples Center!!! I’m HELLA proud."

That same day, the singer also responds to a reaction of the photo on Twitter, saying she is "so lucky to know them" and "they inspire me so much."

We have been friends for almost 2 years! I am so lucky to know them and they inspire me so much. ---- your boys are A+ https://t.co/wsnKKLen1n — h (@halsey) August 7, 2018

Aug. 11, 2018 - Halsey reveals her favorite BTS member

In an rapid-fire interview with MYX Philippines, Halsey is asked for her favorite member of BTS. Halsey replies, "Oh, that’s hard! I can’t pick one," before whispering "RM" into her mic.

March 9, 2019 - Response to a fan

In response to a fan on Twitter who says "I like BTS," Halsey enthusiastically replies, "Me too!!!!!!!!"

March 27, 2019 - Halsey tweets about "Persona" trailer

BTS unveils their first trailer for Map of the Soul: Persona on March 27, featuring RM taking the spotlight to rap "Persona." Halsey is quick to show her support, promptly sharing the link on Twitter with the caption "joon. king."

April 7, 2019 - Teaser for "Boy With Luv" drops

The 45-second teaser shows Halsey operating a ticket window, which she then leaves to find BTS under a bright neon sign labeled "Persona."

April 12, 2019 - Full-circle collaboration drop

Halsey calls it “my pink dream with my pink friends”; BTS simply calls it the video for “Boy With Luv” featuring Halsey, in which the fluorescent-pink-tressed singer contributes chorus vocals and joins the boys for some classic choreographed dance moves.

Amid the ensuing Army tweet-storm, Halsey calls the chorus “sooo addicting” and confesses she has “never done choreo in a video before” but that BTS “made me so comfy and gassed me up.” “Boy With Luv” becomes the most-viewed 24-hour debut in YouTube history, with 74.6 million views. A week later, it debuts at No. 8 on the Hot 100 -- the highest-charting K-pop song by a group of all time.

Thank you! The chorus is soooo addicting! It was stuck in my head for weeks after I left the studio! #boywithluv -- https://t.co/92GyurJ3Xi — h (@halsey) April 12, 2019

May 1, 2019 - The show where it all started

“Boy With Luv” comes to the BBMAs stage when BTS and Halsey perform live together for the first time. Peak friendship achieved!

June 20, 2019 - Halsey praises the BTS ARMY

In an interview with the Zach Sang Show, when asked about her experience with the BTS ARMY following “Boy With Luv,” Halsey says it’s been “so fun,” adding that she feels the fanbase is often misrepresented as being crazy. “They’re the opposite; they’re like intelligent, they’re funny, they’re tasteful, they’re charitable,” she says. “Can you imagine if everyone’s fans thanked them by organizing charity in their names?”

Dec. 3, 2019 - Halsey reveals the track list for her upcoming album Manic

Manic will drop on Jan. 17, 2020, and with it we'll get a new collaboration with Suga ("Suga's Interlude") as the track list shows!

A version of this article originally appeared in the April 27 issue of Billboard.