With a name derived from the first initials of members Sea, Eugene and Shoo, S.E.S. made a monster impact in K-pop throughout the late '90s to early '00s, and is now widely credited for paving the way for all-female acts to take the reigns years later. The trio debuted in 1997 with their sugary single "I'm Your Girl" under record label SM Entertainment, the future home to trailblazing troupes like Girls' Generation and f(x), and took the then-male-dominated industry by storm. The catchy beat, easy-to-follow lyrics and S.E.S.'s schoolgirl image zoomed by other hit makers on the charts -- including boy band sensations H.O.T. and Sechs Kies plus top vocalist Lim Chang Jung. The girls went on to release an extensive list of hits and sell a remarkable amount of records. Although the group disbanded in 2002, the trio's legacy continues today, with S.E.S. still labeled as Korea's best bubblegum novelty."I'm Your Girl"
With an image as sweet as their bubblegum hooks, the nine members of Girls' Generation represent today's softer, effervescent side of K-pop girl groups. With images and concepts that are girly, fun and boast the slightest bit of sex appeal, the nine-piece gained a rabid fanbase that earned them impressive accolades, and became the first girl group to have a music video hit more than 100 million views on YouTube ("Gee"). They also beat out Justin Bieber, One Direciton and Miley Cyrus to win the girls Video of the Year at the inaugural YouTube Music Awards. The act boasts multiple chart-topping albums in both Korea and Japan, while also testing the waters in China and America with Mandarin track "Find Your Soul" and the English single "The Boys" respectively, the latter they performed on "The Late Show With David Letterman" and "Live! With Kelly.""Gee"
Powerhouse group Fin.K.L hit the K-pop scene in 1998 and became S.E.S.'s biggest and only competition -- after all, the group members have stated numerous times that they were deliberately put together by record label DSP Media to rival S.E.S. The quartet -- Lee Hyori, Ock Juhyun, Sung Yuri and Lee Jin -- captured music fans across the nation by successfully pulling off a wide range of musical genres and concepts with ease. From R&B-inspired ballad "Blue Rain" to sweet dance cut "Eternal Love" to the banger "Now," Fin.K.L's string of smash hits helped lead Korea's girl group epidemic until they halted promotions in 2002. The quartet never officially broke up, but have not recorded or released new material since their 2002 LP "Forever." Fin.K.L's leader, Lee Hyori, has since become one of the most successful female solo artists in K-pop history."Blue Rain"
For many outside of Asia, Wonder Girls very likely served as an introduction to K-pop. The retro outfit saw its domestic popularity transfer stateside when they hit No. 76 on the Billboard Hot 100 with the English version of their Korean hit "Nobody" -- three years before "Gangnam Style," mind you. In a controversial move that still divides fans, Wonder Girls' label had the quintet leave Korea at the height of their popularity to focus on learning U.S. culture for a deeper American penetration. While the girls toured America with the Jonas Brothers, released a TeenNick movie and even sang a duet with Stevie Wonder, an English album never surfaced after the Akon collaboration "Like Money" failed to chart. With Korea still happy to support them, the quintet earned two K-Pop Hot 100 No. 1s before announcing a hiatus in February 2013. The group's label insists Wonder Girls has not split up."Nobody"
After School not only stands out as the only girl group in K-pop with an admission-graduation concept, but eventually became known for its incomparable live stage performances. With a lineup that's boasted as little as five members and grown to as big as nine, the group has pulled out everything from tap dances to drum lines to cane dances for TV broadcasts. But After School outdid themselves recently, when the current eight-member lineup trained six months for an athletic pole dancing routine for new single "First Love" (below). The group then showed off its pole-dancing prowess for each TV taping. The girl group represents the true "entertainment" side of K-pop while still boasting a collection of pop music confections."First Love"
If Girls' Generation is K-pop's modern-day Beatles, 2NE1 is its Rolling Stones. With a musical style that opts for attitude-heavy hip-hop, EDM and reggae in place of bubblegum pop, the quartet stood out in K-pop for their fierce attitude and out-there fashion. Along with Wonder Girls and Girls' Generation, the quartet helped spread Korean girl groups internationally, eventually becoming the first female act to play solo U.S. arena shows. While accruing fans like will.i.am -- who featured them on his "#willpower" LP -- and designer Jeremy Scott, the girls cultivated an impressive American fanbase that sent their new album "Crush" to No. 61 on the Billboard 200 -- the highest-charting record for all K-pop acts on the albums charts."I Am the Best"
After weathering through a handful of lineup changes since their official debut in 1997, Baby V.O.X. finally made a huge splash with their third album "Come Come Come Baby" in 1999. Snazzy tracks like "Get Up" and "Killer" shredded the quintet's baby doll image and constructed a cutting-edge look with dark stage ensembles and eye-popping hairdos. The image overhaul, coupled with infectious tracks, helped them shine among their contemporaries, placing "Get Up" and "Killer" on the top of the charts. With their newfound popularity, the group started expanding promotions in and outside of Korea. Baby V.O.X. became the first K-pop group to successfully crossover abroad, notably in China. After finding success in Asia, the girls officially parted ways in 2004."Get Up"
Brown Eyed Girls
The quartet stand out in K-pop girl group history for defying and redefining most conventions that create modern K-pop groups. JeA, Miryo, Narsha and Ga In created Brown Eyed Girls on their own accord, finding each other through friends and mutual respect of one another's talents rather than through auditioning for an agency to be placed in a group -- like every other group on this list. The quartet debuted in 2006 without revealing their actual faces in videos or media, hoping to let their vocals and R&B-inspired ballads speak for themselves. While the ploy didn't lead to huge chart success, the girls came around to embracing their sexuality with a brashness never seen before, most notably with 2009's "Abracadabra" (below) that led to the now-famous hip-swinging dance that PSY incorporated into his "Gentleman" video (which co-starred BEG singer Ga In). The girls have continued to push boundaries with genre-blurring compositions (see "Sixth Sense") and controversial visuals (watch "Kill Bill") with a poise and confidence that satisfies both critics and young fans."Abracadabra"
Although Jewelry went through multiple lineup changes and some setbacks after its 2001 debut, the outfit -- currently promoting as a threesome with members Baby J, Yeown and Semi -- is the longest-running girl group still recording in K-pop today. While the gals made an impressive mark with 2005 single "Superstar," the shining and most significant moment of Jewelry's career came when those same members -- Seo In Young, Park Jung Ah, Baby J and EunJung -- sent their single "One More Time" to No. 1 on all major K-pop digital music charts. The girls blew viewers' minds as they repetitively crooned: "Baby, one more time / Let me blow your mind," in revealing outfits. "One More Time" became the anthem of 2008 and is still the group's most successful single to date.In 2009, members Seo In Young and Park Jung Ah departed the group to pursue individual activities. The remaining recruited new members, Semi and Yewon, released a string of singles with moderate chart success."One More Time"
Known as today's digital-selling monsters in Korea, fourpiece SISTAR has become one of the most consistent groups in K-pop, with hit single after hit single elevating them towards the top of the K-pop girl group rankings. Since the K-Pop Hot 100 introduction in late 2011, SISTAR has the most No. 1s of any group (four), while two members have multiple solo No. 1s (leader Hyorin has three, singer Soyou has two). Meanwhile, the group's splinter duo project Sistar19 -- made up of Hyorin and rapper Bora -- went on to be the biggest hit of 2013. Soyou also tied the all-time chart record when her solo hit "Some" spent six weeks at No. 1 atop the chart. SISTAR is a textbook example of how valuable a girl group can be when each member has charms and skills to ultimately make the entire outfit a supergroup.