When wood gets wet, bad things (such as fungal decay and fastener corrosion) cause wood damage. While it is known these wood damage mechanisms depend upon moisture, a full, mechanistic understanding of how moisture affects these damage mechanisms is still unclear. Recently, Forest Service researchers proposed that these mechanisms depended on the diffusion of ions and other chemicals and developed a model that could explain why wood damage does not occur at dry moisture contents. The Forest Service researchers collaborated with researchers at the Advanced Photon Source at Argonne National Laboratory to perform experiments that could partially validate the model. In these experiments, X-ray fluorescence microscopy was used to develop maps of ion concentration in the cell wall. The results show that diffusion does not occur below a threshold moisture content, which ranged between 60% to 90% relative humidity depending on the ion type and orientation within the cell wall. These promising first results advance our understanding of wood damage mechanisms and also show how X-ray fluorescence microscopy could be used as a tool for understanding treatments that modify wood-moisture relations.