The internet originated in the late 1950s and early 1960s from the development of the ARPANET by the U.S. Department of Defense's Advanced Research Projects Agency. It grew rapidly in the 1980s and 1990s due to the development of TCP/IP and client-server model of network access. By the mid-1990s, the internet connected millions of users worldwide and its growth continued exponentially through the late 1990s and early 2000s with the expansion of commercial internet access and the World Wide Web.