The vision of the Virtual Observatory (VO) is to make access to astronomical databases as seamless and transparent as browsing the World Wide Web is today. It will federate the data flows from current and future facilities and large scale surveys, and the computational resources and new tools necessary to fully exploit them. This requires both technological developments and an international commitment to standardisation and working culture. Increasingly, it will alter the way that astronomers do science, and the way that future facilities and projects plan for their data management, and the scientific exploitation of their data. It will make an impact on a wide variety of astronomical topics, but especially those using very large databases, and those needing a multiwavelength approach, or more generally the use of multiple archives.