Fab labs are shared workspaces containing computer-controlled tools for digital fabrication and mass production. The first fab labs grew out of collaboration between MIT's Grassroots Invention Group and Center for Bits and Atoms to explore how digital information can be physically represented. Popular applications of fab lab tools include 3D printers for plastic or plaster parts, 3-axis CNC machines, printed circuit board milling, and microprocessor design stations. Maker spaces and Maker Faires also provide shared resources for digital fabrication and community collaboration around new technologies. 3D Hubs is an online service that connects users to over 20,000 3D printing locations worldwide, creating an interactive community for 3D printing projects and discussion.