Originally the size of a credit card, soon the miniSIM was introduced and now is called the "standard size". The full-size SIM is no longer used with recent devices -- instead two even smaller variants have been introduced: microSIM and (only used by Apple) the nanoSIM.

^{SIM-Card evolution: full size, miniSIM, microSIM, nanoSIM (Source: Wikipedia)}

Further Links

• SIM Card on Wikipedia (en)