One of the first to break cover is the Oppo X 2021, a concept phone shown off as part of a Oppo's annual future tech expo.
The phone starts off with a standard 6.7-inch OLED display, but this device hides a clever trick – the screen can be rolled out to offer an overall display size of 7.4 inches. You get something (reasonably) small to slide into your pocket, or something bigger to use more like a mini tablet.
And... that's just about all we know about this device. Oppo says it is busy working on components that are solid and robust enough to work time and time again, with a powertrain motor, backing plate and screen laminate designed to last.
LG and TCL are two of the manufacturers also rumored to be working on rollable phones like this one, though we haven't seen any actual hardware yet. We know that LG has the necessary know-how though, as it already manufacturers rollable screens for its premium television sets.
"The screen includes high-precision sensors that conduct real-time monitoring, enabling it to be positioned precisely, and retract and extend smoothly," explains Oppo. A total of 122 patents were applied for during the device's development, with 12 relating specifically to the rolling mechanism. You can see the concept in action in the video below.