Microorganisms in soil play a crucial role in storing carbon, which is important for maintaining healthy croplands. By studying 468 cropland soils in northeast China, researchers found that the amount of carbon in dead microbial cells, as well as the diversity and complexity of the microbial community, are linked to the amount of carbon stored in the soil. For maize fields, the diversity of microbes is key, while for rice fields, the complexity of microbial interactions is more important. Including both microbial community properties and carbon pools in models can better predict soil carbon levels. Improving these microbial factors through management practices could help increase carbon storage in croplands.