A Nano SIM is a small type of Subscriber Identity Module card used in mobile devices. It measures just 12.3mm x 8.8mm, making it the smallest SIM card format 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 replaced the previous Micro SIM format, providing more space for other components in devices. It contains essential information, such as the user's phone number and network details, enabling secure communication and identification on mobile networks.