What do President Obama, Ellen Degeneres and Pope Francis have in common? They’ve all snapped selfies in the last year. So has Miley Cyrus (she’s posted 121 of them on Twitter). Plane-crash survivor Ferdinand Puentes. And astronaut Steve Swanson. And so, I’m nearly positive, have you.

The selfie, of course, isn’t new—it has been around since the advent of photography, when chemist-turned-photographer Robert Cornelius captured one in 1839. But in the past two years, it has become explosively popular—the sort of meme that scales, seemingly overnight, from mere trend to phenomenon to something your Aunt Edna talks about in her crocheting circle. The Oxford English Dictionary called out “selfie” as the 2013 word of the year. More than half of all millennials (age 18-33) have taken a selfie and shared it online, according to a March 2014 Pew Research Center poll. ABC is debuting a new primetime sitcom called Selfie in late September. (Seriously.) Indie band The Chainsmokers produced a music video called #Selfie that became a viral hit (and was awful!). How the heck did these hastily snapped-and-shared self-portraits become le dernier cri of smartphone society?