EPROM silicon chip. Coloured scanning electron micrograph (SEM) of the surface of an EPROM (Eraseable Programmable Read-Only Memory) silicon microchip. The narrow tracks (coloured) that have been deposited on the substrate (grey) form the chip's micro-circuitry. The pits in the tracks are connection points, where connections are made to circuit elements on the other side of the substrate. EPROM chips differ from standard chips in that they can be erased. This is done by removing a protective cover from the top of the chips and exposing the chip to ultraviolet light. The chip can then be reprogrammed. Magnification: x1,400 at 5x7cm size. x3450 at 7 x 4.5 inch size.