Americans who don't speak Korean might not understand the lyrics sung by BTS, an all-male K-pop group, but that hasn't stopped them from becoming obsessed with the music.
BTS was the No. 1 most tweeted about musical group in the U.S. in 2017, according to data from Twitter, topping Justin Bieber, Rihanna and Nicki Minaj. When the group arrived in the U.S. to perform at the 2017 American Music Awards, Ellen Degeneres described the scene in Los Angeles "like the Beatles were here."
At a 2017 BTS concert in Chile, screams from the audience reached 127 decibels, "well past the noise level at which permanent hearing loss becomes a serious concern," according to The New York Times Magazine.
Sunday, the seven-member group re-appeared in the U.S. for the 2018 Billboard Music Awards, mingling with stars like Taylor Swift and John Legend.
But the group's meteoric rise to fame didn't come overnight.
In fact, if the singers — known as Suga, J-Hope, RM, Jimin, V, Jungkook and Jin, who are all in their early 20s — weren't pursuing music, two BTS members say they might be working on a farm instead.
"I might have turned out to be a farmer because I used to do farming when I was in middle school," Kim Seok-jin, known as Jin, tells Billboard in Korean. "My uncle talked me into this."
Kim Tae-hyung, a group member known as V, adds "I also might have been a farmer." (Kim Nam-joon, a BTS member known as Rap Monster, now RM, jokes that Jin would be a famous farmer because of his handsome face.)
The group got its start in 2010, when RM first met Bang Si Hyuk, the group's executive producer and CEO of BigHit Entertainment, based in Seoul.
"I was an underground rapper and only 16 years old, a freshman at high school," RM tells Time. "Bang thought I had potential as a rapper and lyricist, and we went from there."
He learned English as a teenager by watching re-runs of NBC's "Friends," paying careful attention to the subtitles.
"Thanks to my mother, she bought all the season's DVDs," RM says on NBC's "The Ellen DeGeneres Show." "Firstly, I watched with the Korean subtitle. And then next time, I watched it with the English subtitle, and then I just removed it."
BigHit Entertainment held auditions for the other members over two years, and the group debuted in 2013 as Bangtan Sonyeondan, which means Bulletproof Boy Scouts, with their album "2 Cool 4 Skool." Additional members include Jeon Jeong-guk (Jungkook), Jung Hoseok (J-hope), Park Ji-min (Jimin) and Min Yoon-gi (Suga). At that time, the band mates were living in a cramped house and sleeping in one room, according to a video by Korea's K Drama TV.
In 2014, BTS first visited Los Angeles to film a Korean reality show called "American Hustle Life," and were introduced to the culture of hip-hop. Initially, the group's sound was closer to rap than pop, according to Vogue. But in 2015, they began creating more upbeat dance tracks.
Soon, the group had a hit: "BTS as a group sort of took off with the success of our 2015 album that had our hit single 'I NEED U,'" RM tells Time. "We didn't realize we were becoming famous until we were invited to KCONs [K-pop music festivals] in the U.S. and Europe in 2014 or 2015.
"Thousands of fans were calling our name at the venue, and almost everyone memorized the Korean lyrics of our songs, which was amazing and overwhelming," he continues.
That fame extends to South America, according to the New York Times Magazine: For a 2017 concert performance in Chile, 12,500 tickets sold out in two hours. Ticket sales surpassed $2 million.
Revenues at BigHit Entertainment have been doubling annually since BTS debuted in 2013, Bloomberg reported in 2017. And, the company was even considering an initial public offering.
Today, BTS's influence is still growing. The group's latest song, "Fake Love," has racked up 90 million views on YouTube since it was published May 18.
RM attributes the group's success to their vulnerability and emotion: "We talk about our own turmoil and mental breakdowns as honestly as possible in the music and [how] it grows with us as we get older," he tells the Times Magazine.
In their music — often written and produced by themselves — BTS delves into issues like mental health and the class divide.
The group's 2018 album, "Love Yourself: Tear," explores the "dark side" to love and life according to RM. "We sometimes compare ourselves to others and sometimes get really depressed," he tells Entertainment Tonight. "My final goal of my whole life is to love myself."
And that's something you don't need to understand Korean to experience through music, BTS member Suga, says: "I think we can all share in the same message."
Don't miss: Taylor Swift is selling her $2.95 million Beverly Hills mansion — take a look inside
Like this story? Like CNBC Make It on Facebook!
This article has been updated to include the name of Park Ji-Min, and correct Kim Nam-joon's stage name RM.