David, Christopher and Joanna attempt to explain TikTok, the hottest new thing in social media. It's like Vine meets Snapchat meets Instagram meets Spotify, sort of. Then, WSJ reporter Jeff Horwitz comes on to talk about F8, Facebook's annual developer conference, and what to make of all the company's announcements around privacy, messaging, privacy, groups, privacy and payments. Oh, and privacy. In this week's Today I Learned, David explains why motion sickness can be such a problem for VR-and why it's taking decades to fix. Lastly, a dispatch from the TED conference: Reporter Katie Bindley sits down with actor and entrepreneur Joseph Gordon-Levitt to talk about social media, creativity and what happens when you start making decisions just to get more likes.