 From floods and wildfires to land use and invasive species, our ecosystems are constantly changing. The National Ecological Observatory Network, or NEON, is designed to collect data at field sites across the United States to help us better understand these ecosystems and how and why they change over time. The NEON project will transform scientists' ability to study our nation's ecosystems by providing a wealth of open data and a continental-scale infrastructure for research studies. NEON is unique in two ways. First, NEON uses a combination of data collection methods that are spatially integrated within and across field sites. And second, the data collection methods used are standardized across all sites to enable comparisons across the continent. As a result, the data can be used to integrate ecological observations across multiple scales, detect changes in how our ecosystems function, and enable forecasting of environmental change to inform resource management decisions. NEON field sites are strategically located in both terrestrial and freshwater aquatic ecosystems across the United States. They represent the vegetation, landforms, and climates of those regions. At each field site, NEON uses a combination of automated instruments, observational sampling, and airborne remote sensing technologies to collect data that characterize plants, animals, soils, nutrients, freshwater, and atmosphere. NEON's automated instruments collect data 24-7 at terrestrial and aquatic field sites across the nation. Flux towers that rise above the plant canopy at terrestrial sites collect a full profile of atmospheric measurements, along with sensors installed in the ground that monitor soil health. At aquatic sites, a smaller meteorological station collects atmospheric data and other sensors monitor surface water and groundwater quality. In addition to instrument systems, NEON has trained field technicians that conduct standardized sampling throughout the growing season at dozens of plot locations within each field site. They collect organismal and biogeochemical observations that range from plants and animals to soil microbes and aquatic life. Morphology maps of the aquatic field sites are collected, as well as hydrology data to monitor physical changes that occur over time. During peak greenness, NEON's airborne observation platform is flown over field sites to collect hyperspectral, lidar, and high-resolution camera data. These remote sensing systems capture changes to land characteristics like topography, as well as more complex processes like tree growth and forest health across an entire site from year to year. The data collected through these three systems can be studied in conjunction with one another because they're gathered in close proximity to each other at a site. The data are also comparable among field sites, so researchers can study connections and patterns across ecosystems and then develop models to forecast environmental change locally, regionally, and at a continental scale. NEON is an open-science program, which means all NEON data, protocols, and resources are freely available online for anyone to use. Explore NEONScience.org to learn more.