The Plant-Microbe Interfaces (PMI) Science Focus Area (SFA) at ORNL focuses on understanding the physical, molecular, and chemical interfaces between organisms in order to determine their functional roles in biological and environmental systems. Efforts are concentrated on characterizing and interpreting such interfaces using systems comprised of plants and microbes, with particular emphasis on the favorable plant-microbe interactions of the poplar tree (Populus) and its microbial communities. The PMI project seeks to define the relationships among organisms, dissect the molecular signals and genetic responses of the organisms, and interpret this information using advanced computational tools. A specific focus is on understanding and defining the genetic bases of molecular communication between Populus and its microbial consortia within the scope of the plant’s rhizosphere and endosphere in its native environment, which in turn will help define natural routes to managing ecosystem responses to climate change, nutrient cycling and sequestration of carbon in terrestrial environments, and the development and management of renewable energy sources. Capitalizing on prior research on the Populus microbiome, PMI is defining and partitioning the effects of genotype versus environment on the transduction of genetic information and inter-specific signaling. Effective extrapolation of the roles of organisms in complex native settings will require understanding the correlations between inherent characteristics of the organisms involved and the ways that information, energy, and materials are exchanged among and between interacting consortia, including the plant host. The ultimate objective is to understand the exchange of energy, information, and materials across the plant-microbe interface at diverse spatial and temporal scales, a grand challenge in biological and environmental research.