Soils are teeming with billions of microorganisms. Invisible to us, these microorganisms silently work to maintain soil health by breaking down organic matter and recycling nutrients in our environment. Microorganisms also support soil structure and promote plant growth and respond to changing environmental conditions, and in turn impact the overall ecosystem health. The spatial scales at which these interactions occur range from small nanometer scale to large-global scale. Discover who these microorganism are, what they do, why we need microorganisms to maintain healthy soil, and how soil microbiology research is helping inform global ecosystem change.