Since reuniting nine years after their initial disbandment, girl group I.O.I has officially concluded its 10th anniversary activities with flying colors. On May 19, the group released its third EP, I.O.I: Loop, along with the nostalgic title track, “Suddenly,” an ode to the bonds and memories formed since debuting as one of K-pop’s most prolific, yet short-lived, survival show groups in 2016. Now that the group’s promotions have come to an end, let’s take a look at how I.O.I helped transform modern K-pop.

Over the years, project groups have become increasingly popular in K-pop, with some of the industry’s biggest acts being formed from various survival shows. The stipulation to these groups is that they’re often temporary, composed of members from different companies who promote together for a limited time, usually for two years max. However, there was a time when this concept was foreign to most people and considered an unusual strategy for K-pop marketing – until I.O.I came onto the scene and proved that a niche concept could become one of the most powerful tools for securing an established fanbase.

After competing on the Mnet survival show, Produce 101, members Somi, Sejeong, Yoojung, Chungha, Sohye, Jieqiong, Chaeyeon, Doyeon, Mina, Nayoung, and Yeonjung were chosen as the final lineup for I.O.I. On May 4, 2016, the 11-member group debuted with their EP, Chrysalis, and its coinciding title track, “Dream Girls.” The debut was a commercial success, with the mini-album selling over 74,000 copies that year. Meanwhile, “Dream Girls” sold over 530,153 digital copies by July and became the group’s first top-ten single on South Korea’s Gaon Digital Chart.

That success transferred over and intensified into I.O.I’s first comeback with “Whatta Man (Good Man)” in August 2016, which samples American singer Lyn Lyndell’s 1968 hit, “What a Man.” However, rather than featuring all 11 members, the song marked I.O.I's first sub-unit release – a septet consisting of Nayoung, Somi, Chungha, Kyulkyung, Sohye, Yoojung, and Doyeon. Compared to the bright, cute style of “Dream Girls,” “Whatta Man” showcased the group’s more confident and edgy side with its powerful girl-crush energy and sound. As a result, the sub-unit and style switch strategy worked wonders for the group, with the song securing over 2.7 million streams and 128.7k downloads within its first week, making I.O.I the group to watch.

One of the alluring aspects of I.O.I – and many project groups to follow – is that fans have not only watched the members’ journeys but have actively participated and influenced the outcomes of these idols’ careers. Before competing on Produce 101, many of the girls had previously been featured on other survival shows and gained an audience that carried over: Sejeong was a contestant on K-pop Star 2 in 2012, and Somi participated in the survival show Sixteen alongside the members of TWICE in 2015. Some had even been part of other active K-pop groups before joining Produce 101, such as Chaeyeon debuting as a member of girl group DIA in 2015.

Fans get to follow along and vote on which idols and trainees make it into the final lineup, making the process a community effort rather than decisions made behind closed doors by label executives. It’s a shared bond between idols and the fans who have helped make their dreams a reality, which is partly why I.O.I and other project groups tend to thrive in this industry.

In October 2016, I.O.I reached what was arguably the peak of their career with the release of their second EP, Miss Me? and its lead single, “Very Very Very.” Written by former JYP Entertainment CEO J.Y. Park, the track was an infectious electropop earworm fused with elements of bubblegum pop and drum and bass, furthering the group’s sonic landscape. Not only was “Very Very Very” the song to land I.O.I their first music show win, but it became a K-pop phenomenon, garnering over 5.8 million streams in its first week and the No. 1 spot on the Gaon Digital Chart. At this point, the group had fully solidified its place as one of K-pop’s powerhouse acts, despite the ticking time bomb of their one-year contract together almost up.

But it’s not just the charts and streaming numbers that carved I.O.I’s place in K-pop history – they’ve influenced so many little things that have now become staples among idol groups in the industry. One of those examples is the “ending fairy” phenomenon, where idols receive a dedicated close-up at the end of a music show performance and use that brief moment to either catch their breath or show off their charms with a specific pose or action to engage with fans watching at home.

While the term itself was coined in 2013 for EXO’s Xiumin in honor of his fairy-like reactions at the end of music shows, it wasn’t until I.O.I’s Chaeyeon that the trend went viral during her close-up after a performance on Produce 101. Although Chaeyeon didn’t do anything that particularly stood out, it was her visuals and charisma alone that sent the Internet into a frenzy, as she stood there breathing heavily after putting on an energetic performance. The singer and her fancam became so popular, that she was constantly asked to reenact the moment, including during an appearance on SNL Korea.

After that, music shows began adopting the “ending fairy” shot, with girl and boy groups alike putting their own spin on the craze, including doing things like winking, blowing kisses, and even displaying handwritten messages to the fans on paper or with ink on their hands. Now it’s become both a standard practice – where agencies will literally train their idols to prepare ending fairy moments – and a meme, with dozens of artists mimicking and exaggerating the heavy breathing trope that became so popular.

Another trend that I.O.I kicked off and popularized was the M2 Relay Dance, a performance format where members of a group form a single-file line and take turns stepping forward to dance to a portion of their song. The result creates a continuous “relay,” where the members keep it going one by one until the end of the song. As part of their “Very Very Very” promotions, I.O.I became the first group to be featured during the Relay Dance, before the series went on to become a mandatory part of comeback promotions for nearly every group.

Back then, the format was much more laid-back and randomized, where members would often have to dance and lip-sync to parts of a song that were not their own, creating a delightfully chaotic and fun experience for both the idols and fans. Now, the Relay Dance is much more streamlined and planned out ahead of time, with groups taking the performance more seriously as a way to showcase each members’ skills in a unique way. While groups like SEVENTEEN, TWICE, and GFRIEND helped make the series go viral, it wouldn’t have become such a normalized part of the industry if not for I.O.I.

In January 2017, the group released its final single, “Downpour,” before officially disbanding later that month. After the group dissolved, the members went their separate ways and became stars in their own right – many launched successful solo careers, joined separate girl groups, became actresses, and landed brand deals. But as I.O.I approached its 10th anniversary, the members reunited now as women who have grown into their adulthood as experienced individuals. With newfound poise and confidence – but still fun-loving girls at heart – the group’s latest single, “Suddenly,” definitely hits an emotional chord that resonated with longtime fans after all these years.

Not only did the track sweep major music shows, but the group’s offstage promotions through variety shows and online content also created lots of buzz. The reunion is even more poignant now as I.O.I participated in the newer wave of dance challenges that have risen since the group’s debut, including videos filmed alongside industry friends and idols who are now I.O.I’s juniors. Now the group is currently embarking on their newest tour, “I.O.I Concert Tour: Loop,” which was held in Seoul for a three-night stint, before heading off to Thailand, and Hong Kong this month. Needless to say, the group’s long-awaited 10th anniversary comeback was well-received across the board, with both the members and their fans reconnecting in a way that’s genuinely moving and beautifully authentic.