Ecosystem engineers are species that impact their environment in positive or negative ways, through creation, destruction, or modification of habitats. Popular examples are beavers, corals, termites, and woodpeckers. Although largely invisible, fungal networks act as engineers to increase biodiversity and ecosystem resilience by protecting plants. Examples are preventing disease and boosting the ability of plants to defend against insect pests by triggering the production of defensive chemicals. Mycorrhizal fungal networks have shaped life on earth for millions of years and play a major role in engineering our climate. Mycorrhizal networks are also a major carbon sink, which limits global heating. Five hundred million years ago, fungi played a role in the movement of aquatic plants to land by acting as plant root systems, allowing plants to obtain crucial nutrients. These symbiotic associations, which continue today, shaped life on earth, as plant-fungal partnerships coincided with a 90% reduction of atmospheric carbon dioxide. SPUN is working to address this global blindspot: the vast underground networks responsible for sequestering carbon and sustaining life on earth. There are an estimated 450 quadrillion km of fungal mycelium in the top 10cm of earth’s soils.