Discovery Communications, Inc. operates as a non fiction media and entertainment company worldwide. The company provides original and purchased programming across various distribution platforms. Its content covers science, exploration, survival, natural history, sustainability of the environment, technology, docu-series, anthropology, paleontology, history, space, archaeology, health and wellness, engineering, adventure, lifestyles, forensics, civilization, and current events. The company owns and operates nine national television networks in the United States, including Discovery Channel, TLC, Animal Planet, Science Channel, Investigation Discovery, Military Channel, Planet Green, Discovery Fit & Health, and Velocity. Discovery Communications also has interests in Oprah Winfrey Network, a pay-television network and Web site; The Hub that features original programming, game shows, and live-action series and specials; and 3net, a three-dimensional network. In addition, it offers network branded Web sites, and mobile and video-on-demand services; and distributes various national and pan-regional television networks. Further, the company develops and sells curriculum-based products and services to public and private K-12 schools, such as access to an online VOD service that includes curriculum-based tools, professional development services, and student assessment and publication of hardcopy curriculum-based content; and postproduction audio services to motion picture studios, independent producers, broadcast networks, cable channels, advertising agencies, and interactive producers. As of December 31, 2011, it operated approximately 150 distribution feeds in 40 languages. The company is headquartered in Silver Spring, Maryland.