Three years ago, Facebook was the dominant social media site among American teens (ages 13-17). Now only 51 percent of teens use the platform. The most popular social media platforms now are YouTube, Snapchat and Instagram (which is owned by Facebook), according to a new survey by Pew Center Research. Of 743 teens surveyed, 85 percent said they use YouTube, 72 percent use Instagra and 69 percent use Snapchat. Thirty-two percent said they used SnapChat most often, followed by YouTube (32 percent) and Instagram (15 percent). Meanwhile, just 10 percent use Facebook the most. "The social media environment among teens is quite different from what it was just three years ago," the study's lead author Monica Anderson notes. "Back then, teens' social media use mostly revolved around Facebook. Today, their habits revolve less around a single platform."