Wood, like all materials, is composed of atoms. The primary atoms in wood are hydrogen, carbon, and oxygen. It is the organization and interaction of these atoms that control all wood properties like mechanical stiffness and strength. Compared to other engineered materials, such as metals and ceramics, relatively little is understood about how the molecular structure of wood can be modified to control its mechanical properties. A more complete understanding could accelerate efforts to modify wood to be stronger or weaker for specific end uses. Stronger wood, for example, would be desirable for building materials, and weaker wood would be advantageous for biorenergy feedstock because it would take less energy to process the wood into the small chips used in biorenergy processes. Recently, a researcher at the Forest Service’s Forest Products Laboratory in Madison, Wisc.,collaborated with Worcester Polytechnic Institute researchers to combine computer simulation and experimental nanoindentation results to better understand how molecular structure controls wood mechanical properties. New insights gave researchers new information about how the mechanical properties of wood in different orientations are being controlled by its molecular-scale structures. Future work will further identify how the molecular scale structures of wood need to be modified to modify properties in a desired way.