How was the Internet set up?

The internet started being used half a century ago, initially as a network for the American Defense Department. 

Its primary role was to act as a bomb resistant method of exchanging scientific information and intelligence.

In the 1970s and 80s other networks such as the National Science Foundation Network (NSFNET) emerged, linking the net to research agencies and universities.

After the Cold War PCs bacame even more widespread and the Internet grew more publicly accessible and userfriendly by both fans of technology and common people.