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 substantial and sustained investments by governments and companies around the world. In 2000, the United States launched the world's first national nanotechnology program. Since then, the federal government has invested more than $8 billion in nanoscale science, engineering, and technology through the U.S. National Nanotechnology Initiative (NNI). U.S. companies and state governments have invested billions more. As a result of this focus and these investments, the United States has, in the view of many experts, emerged as a global leader in nanotechnology. However, the competition for global leadership in nanotechnology is intensifying as countries and companies around the world increase their investments. Nanotechnology's complexity and intricacies, early stage of development (with commercial pay-off possibly years away), and broad scope of potential applications engender a wide range of public policy issues.