Bistable Displays
Bistable displays have the ability to retain on-screen images even after the power has been turned off.
As the term bistable implies, the picture elements are stable in two (or more) states. The display needs power only when the content changes. Unlike other display technologies bistable displays can use more than one technique to achieve this goal.
For the moment, bistable displays in common use are typically black and white and are used e.g. for such things as retail store signage where the store can change displayed prices from a central location and avoid posting errors.