E-paper, or thin, flexible polymer sheets that look like paper, is thicker than conventional paper and weighs more. E-paper encases microscopic electronic ink particles between two polymer sheets, and the particles display as either white or black in response to an electrical charge. E-paper is reflective and can be read in any light without backlighting or an emissive light source. Power is used only to change content, and the content remains even when power is turned off. Among companies developing commercial applications of E-paper are Gyricon, with its SmartPaper, and E Ink, which produced its first generation e-ink in the Sony Librie e-book reader. With the Librie, users can download and store 500 books of about 250 pages each to the e-book reader, which sized and designed similarly to a paper-back. E Ink and Gyricon have also developed electronic shelf labels that change prices automatically, and e Ink's are wirelessly connected to the store's pricing system. E Ink will develop an advanced smart paper called RadioPaper that not only looks like paper, but also feels like paper. E-Ink is working with the research department at Philips to create thin, flexible, rollable e-paper designed for handheld computers, cell phones, calculators, digital watches, and car dashboards. Fujitsu is developing a paper-like display, with production expected by 2006. E-paper still does not have color, but in about four years, second-generation products will emerge that will probably have improved attributes, lower cost, and more flexibility.