While the Web is the interface, Vint Cerf and Bob Kahn invented the 'language' of the internet: TCP/IP (Transmission Control Protocol/Internet Protocol). On January 1, 1983, ARPANET officially switched to these protocols, marking the birth of the modern Internet. TCP/IP allows different types of computer networks to communicate with each other by breaking data into packets and routing them to the correct destination. This architecture was designed to be decentralized and resilient, originally intended to survive a nuclear strike. This invention turned a closed military and academic project into a global, interconnected 'network of networks' that powers everything from email and streaming to the global financial system and the 'Internet of Things.'