A nano SIM is a small type of Subscriber Identity Module card used in mobile devices. It measures just 12.3 mm by 8.8 mm, making it the smallest SIM card currently available. The nano SIM is designed to fit into modern smartphones and tablets, allowing them to connect to cellular networks for voice and data services. Introduced in 2012, the nano SIM is thinner than its predecessors, the micro SIM and standard SIM. This reduction in size helps manufacturers create slimmer devices while maintaining essential functionality. Many smartphones now exclusively use nano SIMs, making them a standard in the mobile industry.