This research project wants to contribute to the fundamental study of the role which soil pore structure plays in SOM decomposition and stabilization by means of state of the art X-ray (nano) computed tomography and is divided into two parts: i) the exploration and development of X-ray (nano) CT as methdology for visualization of the soil pore structure, the spatial location of SOM herein and the automation of this visualization. Ii) the application of X-ray (nano) CT in combination with a series of incubation experiments to identify pore sizes relevant to SOM decomposition and SOM stabilization.