Apple first introduced the use of the iPad MicroSIM at launch last year. Discharging MicroSIM very helpful in saving space so it can be more places to other components, which in this case is more the place for you. Besides the smaller SIM size also allows Apple to make products that are smaller and thinner. Because of the many advantages that Apple keeps discharging MicroSIM on iPhone and iPad 2.
However the company chief Steve Jobs is felt if MicroSIM currently still could be made into smaller ones. Standard SIM card that is smaller than this are on the ask MicroSIM by Apple to the European Telecommunications Standards Institute (ETSI). If approved then the products Apple later ascertained would wear a card smaller than MicroSIM. But the approval process (if approved) that takes at least a year, so the successor iPhone 4 seems to be wearing a MicroSIM.