Today's teens are a mobile-first generation. They tweet and Snapchat and send over 60 emoji-laden text messages a day. According to Pew, 58% of teens have downloaded apps to their smartphone, and apps like WeChat, Vine, and Instagram take top spots for popularity. So when we set out to launch a mobile app that combines 15 seconds of sound with any digital image, we knew that winning over teens would be essential to our success. Eight months in, we've learned some important lessons about marketing an app to teens. Here are the six keys to success.