Rejoice, photo filter fans, Instagram is heading to Android "very soon," according to founder Kevin Systrom. Speaking at South by Southwest, Systrom raved about the app's growth, boasting of its 27 million registered users. "They're not excited about it because it makes your photos look beautiful," he says, "They're excited because it networks people across the world and it's the single fastest growing thing in mobile period." The Android version is currently being tested in a private beta, and it's reported to be superior than its iOS counterpart. "It's really, really fast," Systrom said. Don't look so surprised, he did tell us, after all, that iOS was just the beginning.