Light micrograph of an integrated circuit used in 'smart cards'. A smart card (or memory card) is a plastic card which contains its own memory chip. The chips are EPROMs (erasable programmable read- only memory). The card (about the size of a credit card) is placed in a reader which supplies power to the chip. The contents of the chip may then be read and altered. The EPROM chip is used as it retains its memory when the power source is removed. Such cards are of use for a variety of information: currently the main application is in personal medical data storage, allowing a person to carry their own medical history at all times. Magnification x10 at 35mm size.