Amazon's portable, handheld reader, which allows users to download digital versions of books, newspapers, and magazines, represents one of the first consumer uses of a low-power, easy-to-read electrophoretic display. The $399 device is a breeze to use, and though the company has not disclosed sales numbers, demand quickly outstripped supply. However, the success of the Kindle may depend on consumers' willingness to bear the price of using it: though e-books, at $9.99, cost less than most physical books, newspapers, blogs, and other content available free on the Internet will cost money (for instance, $1.99 per month for Slashdot and $13.99 per month for the New York Times).

1. Electronic paper
The Kindle's 600-by-800-pixel, 167-pixels-per-inch screen uses a display technology made by E Ink of Cambridge, MA. At the front of the screen is a layer of transparent electrodes. Below it are millions of microcapsules containing positively charged white particles and negatively charged black particles, and below them is a layer of nearly a million more electrodes. A negative charge on one of these bottom electrodes pushes black particles to the top, and a positive charge does the same with the white ones. Each microcapsule acts as a pixel that can thus be made to appear black, white, or gray.