Stephen Crocker and Vinton Cerf were among the graduate students who joined UCLA professor Len Kleinrock in an engineering lab on September 2, 1969, as bits of meaningless test data flowed silently between two computers. By January, three other "nodes" joined the fledgling network.
Then came e-mail a few years later, a core communications protocol called TCP/IP in the late 1970s, the domain name system in the 1980s, and the World Wide Web -- now the second most popular application behind e-mail -- in 1990.
The trio did not realize at the time that they had invented what would eventually become a multi-billion dollar business. Crocker and Cerf still are involved in Internet-related activities.
You can find an excellent article describing all this on CNN. The same article gives a small peek into Internet2, which is already operational although most people have never heard of it.