The U.S. Department of Energy (DOE) is a cabinet-level department charged with national security, research and development, and economic and environmental missions related to energy and energy technologies. Historically the department's missions and budget have emphasized nuclear energy, especially nuclear weapons production and related activities. The department's broader mandate encompasses activities across a wide range of areas including fossil fuels, renewable and alternative energy sources, energy infrastructure, environmental management, and fundamental and applied research. With a budget exceeding $24 billion and more than 100,000 federal and contractor employees, the DOE is a large and complex organization affecting many aspects of environmental and energy politics.