With this experimental context in mind, the current study aims to use the power of molecular simulation to act as a computational microscope to identify how interactions in intact biomass respond to changes in hydration (Figure ). Using prior experiments as a benchmark for comparison , we can compute diffusion coefficients for multiple ion species (Na + , K + , Cu 2+ , and Cl -) within our models. We find that the diffusion coefficients determined from atomistic simulation models show the same trends found experimentally. Using the detailed structural information available only from an atomic model, we find that increasing hydration reduces contacts between individual biopolymers within a cell wall, creating the space for rapid diffusion along hydrated tracks parallel to the hemicellulose strands once water molecules account for 10-15% of the total mass for the cell wall. The detailed molecular picture also identifies interactions between carboxylate groups that decorate the hemicellulose and positive ions. These interactions impede diffusion even further beyond what the crowded conditions require within the cell wall.