In human–computer interaction, an organic user interface (OUI) is defined as a user interface with a non-flat display. After Engelbart and Sutherland's graphical user interface (GUI), which was based on the cathode ray tube (CRT), and Kay and Weiser's ubiquitous computing, which is based on the flat panel liquid-crystal display (LCD), OUI represents the third wave of display interaction paradigms, pertaining to multi-shaped and flexible displays. In an OUI, the display surface is always the locus of interaction, and may actively or passively change shape upon analog (i.e., as close to non-quantized as possible) inputs. These inputs are provided through direct physical gestures, rather than through indirect point-and-click control. Note that the term "Organic" in OUI was derived from organi