A gyricon sheet is a thin piece of transparent plastic that contains millions of small beads. Each bead--half white half black--is contained in an oil-filled cavity and is free to rotate within its cavity.
Epaper is electrically writable and erasable and can be re-used 1000s of times. When voltage is applied to the surface of the sheet, the beads rotate to display either their black sides or white sides. Images of pictures and text are created when a pattern of voltages are sent to the paper. The image will remain until the voltage pattern changes.