together with other players and create bigger and more intricate environments. These environments can then be accessed by other players, if the server is available to other players then they may be able to modify parts of it, such as the structure of the environment. At one level, a more or less realistic rendered 3D space like the game world of Halo 3 or Grand Theft Auto V is just as much a big database as Microsoft's Encarta encyclopedia. Use in education Virtual worlds represent a powerful new medium for instruction and education that presents many opportunities but also some challenges. Persistence allows for continuing and growing social interactions, which themselves can serve as a basis for collaborative education. The use of virtual worlds can give teachers the opportunity to have a greater level of student participation. It allows users to be able to carry out tasks that could be difficult in the real world due to constraints and restrictions, such as cost, scheduling or location. Virtual worlds have the capability to adapt and grow to different user needs, for example, classroom teachers are able to use virtual worlds in their classroom leveraging their interactive whiteboard with the open-source project Edusim. They can be a good source of user feedback, the typical paper-based resources have limitations that Virtual Worlds can overcome. Multi-user virtual worlds with easy-to-use affordances for building are useful in project-based learning. For example, Active Worlds is used to support classroom teachers in Virginia Beach City Public Schools, the out-of-school NASA RealWorld-InWorld Engineering Design Challenge, and many after school and in school programs in EDUni-NY. Projects range from tightly scaffolded reflection spaces to open building based on student-centered designs. New York Museums AMNH and NYSci have used the medium to support STEM learning experiences for their program participants. Virtual worlds can also be used with virtual learning environments, as in the case of what is done in the Sloodle project, which aims to merge Second Life with Moodle. Virtual worlds allow users with specific needs and requirements to access and use the same learning materials from home as they would receive if they were physically present. Virtual worlds can help users stay up to date with relevant information and needs while also feeling as they are involved. Having the option to be able to attend a presentation via a virtual world from home or from their workplace, can