Often the technologies that reshape daily life sneak up on us, until suddenly one day it's hard to imagine a world without them--instant messaging, for example, or microwave ovens. Other watershed technologies are visible a mile away, and when you contemplate their applications, the ultimate social impact looks enormous. A good example of the latter is radio frequency identification chips--RFID, for short.

An RFID chip is a tiny bit of silicon, smaller than a grain of rice, that carries information--anything from a retail price, to cooking instructions, to your complete medical records. A larger piece of equipment called an RFID "reader" can, without direct contact, pull that information off the chip and in turn deliver it to any electronic device--a cash register, a video screen, a home appliance, even directly onto the Internet. RFID is the technology used now to automate toll taking at bridges and tunnels; drivers are given a small plastic box with an RFID chip inside, allowing them to drive through the tollgates without stopping. An RFID reader in the tollbooth senses the information on the chip and the toll is automatically deducted from the driver's account.

The first wide-scale applications of RFID will be in retail. At a major industry conference next week, Wal-Mart is expected to urge its suppliers to adopt RFID--the same way that, twenty years ago, the giant retailer jump-started the use of bar codes. And some manufacturers are already on board. Gillette, for example, recently placed an order for half a billion RFID chips that they will begin to use to track individual packages of razors.（264 words）