Right now, somewhere in Stuttgart, Germany two adorable, blonde identical twins named Lisa and Lena are recording a 15-second video that will reach almost 5 million people. This isn't very shocking in a post-Facebook world made much smaller by social media. What is surprising, however, is that the app of choice for these two 15-year-olds is not Snapchat or Facebook or even Instagram. Rather, it's an app called Musical.ly that has over 90 million users, many of them teenagers, which explains why even if the tech world has taken notice, the mainstream hasn't just yet.

Launched in 2014, Musical.ly was recently valued at $500 million for its rapidly trending videos and ever-increasing audience. The app allows users to easily record themselves lip-synching to their favorite songs, but sets itself apart with the addition of unique video effects like time lapse, which makes everyone's dance moves look as fast as Looney Toons.

Lisa and Lena created their account last fall. They much prefer it over the other social media alternatives.

"We can be like actors and be creative," explained Lena of the twins' extremely well-coordinated moves and passionate lip-synching. In a short time, their videos gained them an enormous following, nearly 4.7 million fans and counting.

Their recent rendition of Gnash's "I Hate You, I Love You" alone, which they did for the app homepage #EmotionChallenge, received almost 3 million views. In sum, they gritted their braces with closed eyes and it was as emotional as any 15-second video could be.

Before posting, Lisa and Lena discuss outfits ("not too much makeup") and practice their coordination. They then film using the app's technology that slows down the music of choice, allowing users to really nail their moves. Finally, they show the video to their parents for approval.

"We are always excited and a bit nervous to post a new Musical.ly video because more and more people watch it," said Lena - the sisters prefer to keep their surname private because of their age. "Some people at school cannot understand the fact that we are somewhat 'famous' all of the sudden."

"We are a bit of a topic at school," echoed Lisa.

While Lisa and Lena have certainly solidified their spot on the app's "leaderboard," they share the spotlight with other teenagers like Vine-star-turned-Musical.ly-star Jacob Sartorius, who has 7.03 million fans and his own hit single called, "Sweatshirt." And @BabyAriel, whose robotic hand movements are impeccably synched to Rihanna songs.

A dancer named Mackenzie Davis, also known as @RaddestRedhead, reached over half a million on the app and over 1 million on Instagram for her choreography to Drake's "One Dance." And then there's real-life celebrities like Ariana Grande and Jason Derulo, who've used to app to promote their own music.

Musical.ly "leaders" argue that unlike Snapchat and Facebook, Musical.ly requires not only tech savvy, but also a certain level of skill, and certainly time commitment. These are not throw-away videos, but may be in fact be birthing an entirely new medium, much like Vine and Snapchat did.

On the app, you've got to have a talent for movement, coordination, and performance to make it to the top. Or as a teen would say, "Moves like Jagger."

On second thought, someone should tell Mick Jagger to join.