With the debut of SM Entertainment's latest girl group, Red Velvet, it's worth taking a glance at where SM's power groups Girls' Generation and f(x) were at the time of their debut.

Even though being part of SM Entertainment means that idol groups will get a lot of publicity, both of SM's star girl groups struggled for some time before becoming popular. Their songs were well known, but Girls' Generation's "Gee" was the group's first real chart-topper, and f(x) only begun to win awards with Danger."

Girl's Generation debuted in 2007.  Gee's debut song "Into The New World" came out in August 2007. Although it wasn't immensely popular, "Into The New World" reached number one on M! Countdown, and gained a lot of attention.

Girls' Generation had a number of small successes,  such as with "Kissing You," and promoted like any other rookie group.

 When the song was released, the "Gee" dance became famous, in part due to the trend of K-Pop dances becoming popular thanks to being uploaded internationally on YouTube (The Wonder Girl's song "Tell Me" is similar.) 

f(x) debuted in 2009, with "LA ChA TA," but the song didn't really do so well.  It took until 2011 for the group's song "Danger (Pinocchio)" to start winning on award shows.

"Nu (ABO)" had gained popularity prior to it, setting up the stage for "Danger," but it also took two years for f(x) to gain true popularity.  Now, however, f(x)'s songs almost always receive a lot of love, as seen recently with "Red Light."

That being said, while both Girls' Generation and f(x) took two years to reach the upper echelons of K-Pop, it's impossible to say what will happen with Red Venus. SM Entertainment's latest boy band EXO debuted to a huge amount of fame, and hardly was able to be called a rookie group.

Red Velvet's gained a lot of attention, both good and bad, for debuting this summer. If they're like other recent SM rookie girl groups, then they'll take their time before a hit. However, nothing is clear in the current K-Pop industry.