A foldable phone is a smartphone with a folding form factor. Some variants of the concept use multiple touchscreen panels on a hinge, while other designs utilize a flexible display. Concepts of such devices date back as early as Nokia's "Morph" concept in 2008, and a concept presented by Samsung Electronics in 2013 (as part of a larger set of concepts utilizing flexible OLED displays), while the first commercially available folding smartphones with OLED displays began to emerge in November 2018. Some devices may fold out on a vertical axis to into a wider, tablet-like form, but are still usable in a smaller, folded state; the display may either wrap around to the back of the device when folded (as with the Royole FlexPai and Huawei Mate X), or use a booklet-like design where the larger, folded screen is located on the interior, and a screen on its "cover" allows the user to interact with the device without opening it (such as the Samsung Galaxy Z series). Horizontally-folding smartphones have also been produced, typically using a clamshell form factor.
