microSD is a kind of removable flash memory card used for storing information. SD is an abbreviation of Secure Digital. An SD card is a solid-state device. This means it has no moving parts in order to function. Inside the SD card is circuitry that includes flash memory. Flash memory is a type of EEPROM chip as mentioned in #2. It has a grid of columns and rows with a cell that has two transistors at each intersection. The two transistors are separated from each other by a thin oxide layer. One of the transistors is known as a floating gate, and the other one is the control gate. The floating gate's only link to the row, or wordline, is through the control gate.