Apple reminds iPhone X owners they're using an OLED display
 

Apple's bezel-less "X" is the first iPhone with an OLED screen -- a technology known for its greater contrast and saturation, but also for its tendency to get burn-in. To make sure customers understand that their $1,000 phone might suffer from image...
https://www.engadget.com/2017/11/04/...d-on-iphone-x/