Ectomycorrhizal symbioses are among the most widespread associations between roots of trees and soil fungi in forest ecosystems and contribute significantly to the sustainability of forest ecosystems through nutrient cycling and carbon sequestration. Due to increasing genomic and transcriptomic resources and the development of new tools for functional characterization, significant progress has been made in understanding the establishment and functioning of this mutualistic interaction. Here we summarize our current knowledge about the evolution of ectomycorrhizal symbiosis, the signaling and communication necessary for the development of the plant-microbe interface and how nutrient exchange will affect the association, from both the plant and fungal perspective.