Nanotechnology is research and development that involves measuring and manipulating matter at the atomic, molecular, and supramolecular levels at scales measured in approximately 1 to 100 nanometers (nm) in at least one dimension.”Materials at such small scales often exhibit different electrical, magnetic, optical, mechanical, and other physical properties from their bulk material counterparts, leading to the development of potentially revolutionary technologies in a variety of industries,including agriculture and food. By increasing productivity, reducing postharvest loss, improving product quality, increasing the competitiveness of agricultural producers, and improving market access, advances in nanotechnology may present new opportunities to improve the livelihoods of the poor. But nanotechnology may also create new risks.Investments in agriculture and food nanotechnologies carry increasing weight because their potential benefits range from improved food quality and safety to reduced agricultural inputs and improved processing and nutrition. While most investment is made primarily in developed countries, research advancements provide glimpses of potential applications in agricultural, food, and water safety that could have significant impacts on rural populations in developing countries.Despite their promise, agricultural and food nanotechnologies, especially those that could reduce poverty or increase food and nutrition security, will likely face many challenges in each step of development—from investment in research and development (R&D) to adoption and use—before being commercialized and used by the rural poor. Many of these obstacles appear in the development of any new technology, but there are also issues specific to nanotechnology: intellectual property rights (IPR), the management of safety and environmental risks in the presence of wide uncertainties, and possible market displacement effects induced by these technologies, among other concerns. This brief presents a review of the potential opportunities and challenges of using nanotech applications for agriculture, food, and water in developing countries.