Answer: Liquid Crystal Display
Liquid crystal displays are used for everything from calculator displays to monitors to portable video game units. The displays are created by sandwiching a layer of liquid crystals (the specific kind of liquid crystal used varies depending on the application) between layers of electrically conductive polymer and glass, which is then covered by layers of polarizing filter film.
The layer of electrically conductive polymer can be simple (like the display of a basic calculator) or quite complex (like the panel used for a computer monitor or television). Current is run through the conductive material to toggle portions of the panel on and off in order to manipulate the output. LCD screens, unlike other display technology such as CRT monitors, do not generate their own light and usually require back-lighting—commonly CCFLs or LEDs—for comfortable use.
Although the displays we use today feel distinctly modern (and certainly employ sophisticated modern technology), the history of liquid crystal displays dates all the way back to the 19th century. There, the research of Friedrich Reinitzer in the 1880s laid the foundation for the industry with his discovery of the liquid crystalline nature of cholesterol extracted from carrots. In 1911, Charles Mauguin experimented with liquid crystals confined between plates in thin layers, and by the late 1920s, Vsevolod Frederiks had devised an electrically switched valve to control the passage of light through the liquid crystals. Further refinements in the 1960s led to the explosion of simple monochromatic LCD displays on watches, calculators, and other devices in the 1970s.