With the advent of the internet and the World Wide Web we are able to share information as never before. The Web has become a critical global infrastructure. Since its emergence in the mid-1990s, it has exploded into hundreds of billions of pages that touch almost all aspects of modern life. Today the jobs of more and more people depend on the Web. Media, banking and health care are being revolutionized by it, and governments are even considering how to run their countries with it. Little appreciated, however, is the fact that the Web is more than the sum of its pages and it is more than its technical protocols. Vast emergent properties have arisen that are transforming society. E-mail led to instant messaging, which on the Web has led to social networks such as Facebook and Twitter. The transfer of documents led to file-sharing sites such as Napster, which have led to user-generated portals such as blogs, Flickr and YouTube. Web 2.0, tagging content with labels, is creating online communities that share everything from concert news to health care. Looking forward we are adding to the Web of documents by creating a Web of linked data. It is our hypothesis that this will become the dominant data sharing and integration platform and that its effect on the world will be as profound and unexpected as the impact of the first Web. As we seek to understand the origins of the Web, appreciate its current state and anticipate possible futures there is a need to address the critical questions that will determine how the Web evolves as both a social and a technical network. The emerging field of understanding these issues is becoming known as Web Science. In this talk we will explore how this new science of the Web has become established, the insights that are beginning to emerge and discuss the major research and education challenges ahead.