Only six social media apps in the world have a billion or more users, and four of them belong to Facebook. Tops is the eponymous flagship app, known as “Big Blue,” followed by three apps all focused on messaging: Instagram, WhatsApp, and Messenger. So when Facebook decided to do a significant redesign of the latter—currently used by 1.

Get in-depth coverage of current and future trends in technology, and how they are shaping business, entertainment, communications, science, politics, and society.