Nanotechnology -- a term encompassing the science, engineering, and applications of submicron materials -- involves the harnessing of unique physical, chemical, and biological properties of nanoscale substances in fundamentally new and useful ways. The economic and societal promise of nanotechnology has led to investments by governments and companies around the world. In 2000, the United States launched the world's first national nanotechnology program. From FY2001 through FY2013, the federal government invested approximately $17.9 billion in nanoscale science, engineering, and technology through the U.S. National Nanotechnology Initiative (NNI). President Obama has requested $1.7 billion in NNI funding for FY2014. U.S. companies and state governments have invested billions more. The United States has, in the view of many experts, emerged as a global leader in nanotechnology, though the competition for global leadership is intensifying as countries and companies around the world increase their investments. Nanotechnology's complexity and intricacies, early stage of development (with commercial payoff possibly years away for many potential applications), and broad scope of potential applications engender a wide range of public policy issues. Maintaining U.S. technological and commercial leadership in nanotechnology poses a variety of technical and policy challenges, including development of technologies that will enable commercial scale manufacturing of nanotechnology materials and products, as well as environmental, health, and safety concerns. This book provides an overview of nanotechnology, the National Nanotechnology Initiative, possible reauthorization of the 21st Century Nanotechnology Research and Development Act of 2003 (P.L. 108-153), and appropriations issues.