A micro SIM is a type of subscriber identity module card used in mobile devices. It is smaller than the standard SIM card, measuring 15mm x 12mm, and is designed to fit into devices that require a more compact size. Micro SIMs store essential information, such as the user's phone number and network details, allowing the device to connect to cellular networks. Introduced in 2003, the micro SIM was developed to accommodate the growing demand for slimmer and more efficient mobile devices. Many smartphones, including those from Apple and Samsung, utilize micro SIMs, making them a common choice for users seeking enhanced performance and portability in their devices.