All these girls are in their early 20's. Their debut was in 2007 which means that they debuted when they were in senior or junior high school. Before their debut all of them have to go through long period of training. The shortest period is 2 years. Most of them trained for more than 4 years. During their training they are not only learning about singing and dancing but they also have to learn to speak different languages; Japanese, English. All the K-Pop stars are most likely going through these steps like 2ne1, Big Bang, Super Junior, Shinee etc.
You cannot imagine their popularity in Korea let me rephrase that in "Asia".
Now these girls are slowly conquering America and Europe. Two weeks ago they debuted through David Letterman's late night show and Kelly Morning show. Check it out on YouTube. Fans are going crazy to see them. It is insane. I didn't expect that they will be this big.
Their popularity starts spread around the world like cancer (in a good way tho). They are like Olympic stars that represents (South) Korea and becoming the (South) Korean Pride.
Try to check out k-pop music on billboard chart or allkpop website to see more.
