This chapter gives an introduction into the smart card technology and its history by outlining the role of the smart card in mobile communications systems. The role of the smart card as a key enabler for services requiring or utilizing unambiguous user-identification is outlined. These services include multimedia and high-security services such as mobile commerce or mobile banking. Smart cards containing the described mechanisms provide the user with privacy and the capabilities to use information, personalized according to his needs, in a wide-spread system with a virtually unlimited number of services. Furthermore, the capabilities of the smart card to enhance services, to secure the issuers’ revenues and to increase the usage of the services by providing a trustful platform for the user are described. Future evolutions and further developments of the smart card are illustrated, including how they pave towards new types of applications and services.