Soil organic matter (SOM) stores more than three times as much carbon as the atmosphere or terrestrial vegetation, yet its long-term persistence remains poorly understood. Recent research shows that molecular structure alone does not determine SOM stability; instead, environmental and biological factors play a dominant role. This understanding is crucial for improving predictions of how soils will respond to climate change. The persistence of SOM is primarily an ecosystem property, influenced by physicochemical and biological interactions in the soil environment, rather than the intrinsic properties of the organic matter itself. Key insights include the role of environmental conditions in controlling decomposition rates, the importance of microbial inputs in SOM cycling, and the influence of soil structure and physical disconnection on carbon turnover. Fire-derived organic matter, though initially thought to be stable, can decompose over time. Deep soil carbon, which constitutes a significant portion of global soil carbon stocks, is vulnerable to decomposition, particularly in thawing permafrost regions. The stability of SOM is also influenced by factors such as soil acidity, redox conditions, and the presence of decomposers. Recent advances in analytical techniques have challenged traditional views of SOM stability, emphasizing the need for new models that incorporate these factors. The integration of molecular, biological, and physical data is essential for developing more accurate predictions of soil carbon dynamics. Future research should focus on long-term experiments, interdisciplinary collaboration, and the development of new models that account for the complex interactions governing SOM stability. These efforts are critical for understanding and managing soil carbon cycles in the context of global environmental change.Soil organic matter (SOM) stores more than three times as much carbon as the atmosphere or terrestrial vegetation, yet its long-term persistence remains poorly understood. Recent research shows that molecular structure alone does not determine SOM stability; instead, environmental and biological factors play a dominant role. This understanding is crucial for improving predictions of how soils will respond to climate change. The persistence of SOM is primarily an ecosystem property, influenced by physicochemical and biological interactions in the soil environment, rather than the intrinsic properties of the organic matter itself. Key insights include the role of environmental conditions in controlling decomposition rates, the importance of microbial inputs in SOM cycling, and the influence of soil structure and physical disconnection on carbon turnover. Fire-derived organic matter, though initially thought to be stable, can decompose over time. Deep soil carbon, which constitutes a significant portion of global soil carbon stocks, is vulnerable to decomposition, particularly in thawing permafrost regions. The stability of SOM is also influenced by factors such as soil acidity, redox conditions, and the presence of decomposers. Recent advances in analytical techniques have challenged traditional views of SOM stability, emphasizing the need for new models that incorporate these factors. The integration of molecular, biological, and physical data is essential for developing more accurate predictions of soil carbon dynamics. Future research should focus on long-term experiments, interdisciplinary collaboration, and the development of new models that account for the complex interactions governing SOM stability. These efforts are critical for understanding and managing soil carbon cycles in the context of global environmental change.