Memory Stick is a removable flash memory card format, launched by Sony in October 1998, and is also used in general to describe the whole family of Memory Sticks. This family includes the Memory Stick Pro, a revision that allows greater maximum storage capacity and faster file transfer speeds; Memory Stick Duo, a small-form-factor version of the Memory Stick (including the Pro Duo); and the even smaller Memory Stick Micro (M2). In December 2006 Sony added the Memory Stick Pro-HG, a high speed variant of the Pro, to be used for high definition still and video cameras.
The original memory stick was available in sizes up to 128 MB, and a sub-version, Memory Stick Select allows two banks of 128 MB to be on the same card. An 8 GB card was unveiled at the 2006 Consumer Electronics Show in Las Vegas, but according to Sony the Memory Stick Pro has a maximum potential size of 32 GB. *quoted from Wikipedia.