Mobile and cloud computing have emerged as the new computing platforms and are converging into a powerful cloud-mobile computing platform. This article envisions a virtualized screen as a new dimension in such a platform to further optimize the overall computing experience for users. In a virtualized screen, screen rendering is done in the cloud, and delivered as images to the client for interactive display. This enables thin-client mobile devices to enjoy many computationally intensive and graphically rich services. Technical challenges are discussed and addressed. Two novel cloud-mobile applications, Cloud Browser and Cloud Phone, are presented to demonstrate the advantages of such a virtualized screen.