In one teaspoon of soil, we can find more than 5,000 species of bacteria, fungi, nematodes and other microbial organisms. Such “soil biota” support a wide range of functions, such as nutrient cycling and water regulation and purification. Yet it is challenging to define how soil organisms contribute to these soil functions. A new framework can help us understand the complexity of soil biology in relation to multiple soil functions. The framework is supported by an online tool that enables users to better select methods for assessing soil quality.