Remember how innocent Sunmi was when she was with the Wonder Girls back in 2007? Shortly after their debut, they really struck the charts with their funk-pop song "Tell Me." Sunmi's girly outfits and cutesy facials during her "Tell Me" Days is in stark contrast to the sexy-icon image she's established as a solo artist with songs like "24 Hours" and her most recent release, "Gashina."

Yes, even this sexy queen also had the days of wearing pigtails and huge hair buns as a leader of the '90s girl group Fin.K.L. While Lee Hyori dominated as the sexy diva of K-Pop from the very beginning of her solo career with "10 Minutes." But she's since undergone another complete transformation after getting married to her husband, musician Lee Sang Soon. Lee Hyori has definitely toned the "sexy" down. From the music videos to live performances, makeup, and the outfits, the overall look for her latest album is much more monochrome and less glitz and glam.

Girls Day adapted the sexy concept after their earlier promotions didn't perform very well. Their earlier songs -- from their debut with "Tilt My Head" to "Twinkle Twinkle" and "Hug Me" -- featured more colorful, playful outfits and cutesy choreography. They even tried a pop-rock theme with their song "Nothing Lasts," but that didn't do very well either. But this girl group finally struck high on the music charts with releases like "Expectation" and "Something," channeling their sexy side with more revealing, skin-tight outfits and sultry choreography.

Sonamoo debuted with "Deja Vu" in 2014, a track that drew inspiration from hip-hop, from the hard beats to the all-black outfits. But their songs have since become more colorful and bubbly, like "I Think I Love You."

Dalshabet's debut with "Supa Dupa Diva" was colorful and youthful. But they've since done a complete 180-spin into the sexy concept, with revealing outfits and steamy, sexually suggestive choreography. In fact, their 2015 release "Joker" was even banned by KBS in part because of the revealing choreography.

Rainbow is actually the opposite of Girls Day and Dalshabet. They debuted with a sexy concept with the song "A," with their sharp cat-eyeliner and choreography in which they lift their shirts and bare their abs. But they've taken on a cuter concept with their later releases. It's a shame they disbanded!

This group shows off their girly, youthful flare donning school uniform-like outfits and pigtails in their debut song "High Heels." But they did a complete twist with their girl-crush, badass concept in "Hobgoblin" with their hard-hitting, sexy choreography, street, hip-hop-inspired outfits and darker makeup.

The girls did a complete transformation with their song "Fingertip." The badass girl image with the sexier outfits and choreography contrasts the cuter, girl-next-door concept of their other songs like "Me Gustas Tu."

Spica is, unfortunately, one of the groups that seem to be simply confused about what concept they should take on. They debuted with more ssen-unnie concepts with the song "Russian Roulette," then went to funky with " inspired by their label mate senior Lee Hyori took on a more hippie concept with "Tonight." But nothing seems to have been a huge success for them.

When they debuted with "Replay" they gave off the image of cute younger boys -- especially Taemin -- trying to play it cool to flatter older girls -- they literally sang, "Nuna you're so pretty" in the song. But they've increasingly taken on sexier concepts with their later releases like "Sherlock" and more recently, "View."

Jay Park has gained the most prevalence for his hip-hop, R&B hits, and appearances as a producer on "Show Me the Money." But don't forget, even Jay Park started out as an idol, as the leader of 2PM!

Zico walked the same path as Jay Park -- check out his Block B with "Freeze." From the techno beat to the robotic choreography, to the metallic outfits and makeup, this is a completely different look from the Zico we see now. But also in general, Block B transformed completely since their debut adapting more hip-hop like their song, "Nillili Nambo."

When this group debuted with "Boyfriend," they were the epitome of the lovable, cutesy concept, with their bright outfits and cheesy choreography. But the bring out their sexiness in the song "Obsessions" with their all-black outfits and sexier choreography.

Big Bang did basic hip-hop and pop when they first debut with melodies like "La La La" but they have changed their concepts with much more sophisticated themes over the years. The best example I think would be "Fantastic Baby."