The National Ecological Observatory Network (NEON) focuses on grand challenge questions in environmental science relevant to large regions that cannot be addressed with traditional ecological approaches. These challenges involve: (1) understanding and predicting the way ecosystems work and respond to changes, especially at large scales; (2) understanding how ecosystem processes feed back to alter Earth System processes, including climate and hydrology; and (3) understanding the implications of these processes and feedbacks for the human endeavor. NEON will be an NSF-sponsored research facility for the study of long-term, large-scale ecological change. The goal of NEON is to enable understanding and forecasting of the impacts of climate change, land use change and invasive species on continental-scale ecology by providing infrastructure to support research in these areas.