MicroSD
It is the smallest memory card that can be bought; at 15 mm × 11 mm × 1 mm (about the size of a fingernail), it is about a quarter of the size of a normal-sized SD card. There are adapters that make the small microSD able to fit in devices that have slots for standard SD, miniSD, Memory Stick Duo card, and even USB. But, not all of the different cards can work together. Many microSD cards are sold with a standard SD adapter, so that people can use them in devices that take standard SD but not microSD cards.