Its exact date of birth is not quite certain but the general consensus（一致，合意） is that October 29, 1969 was when it really started.
On that day, engineer and computer scientist Leonard Kleinrock and his colleagues watched with excitement as a big grey box was delivered to their laboratory at University of California Los Angeles (UCLA).
The box - the size of a fridge - was then connected with a computer that would make contact with another computer several hundreds miles away at the Stanford Research Institute.
Undergraduate Charley Kline was given the simple job of logging on remotely from UCLA to the SRI machine; his one command was "login".
The first attempt, however, proved too much for the "interface message processor（信息接口处理器）" or IMP for short - the system crashed as young Charley reached the letter "g".
It was a slow build up with, 12 years on, only 213 computers being linked up to the network.
In 1985 things were looking up with 16 million people going on through email.
But it was with the arrival of web browsers that the idea really took off, with more than 513 million people online by 2001.
To date（到目前为止）, around 1.7 billion people are connected to the Internet.
And what of the future?
Peter Buckley, author of the Rough Guide to the Internet said "now" is a very exciting time.
"We're on the edge of cloud computing（云计算） which basically means we're migrating from computer-based programs such as Word and Outlook to Internet-based systems such as googlemail or whoever.
"What it means is that our information is now held in the ether, rather than on the computer. There are security risks of course although the Internet service providers are always working hard to ensure data is protected.
Ruth Barnett, Sky News' Twitter Correspondent says: "It is difficult to predict the future as we have seen so many unexpected innovations already, and surely no one could have realized 40 years ago how substantially it would change the way we live.
"It could become increasingly creative, open and collaborative（合作的）, or we could become more and more "tethered（被束缚的）" to the companies who make the gadgets（小工具） we use to access it - such as phones or games consoles.
"There'll always be developments hyped（宣传，炒作） as the 'next big thing' from online shopping to Twitter to iPhones. But what I think will endure is the appetite（欲望，胃口） to connect and share information, on the go."