The #10YearChallenge is simple: post a photo of yourself in 2009 beside a current 2019 one. Many people have taken the opportunity to gloat and show off their agelessness . Others have used it as a moment to show just how significant their glow-up has been, to varying degrees of hilarity. There's even a theory that all of these then-and-now split-screen photos will one day be mined by Facebook to train a facial recognition algorithm on age progression. Celebrities have gotten creative with the meme and tailored it the way they want, to the delight — and sometimes, horror — of fans.