The goal of this project was improve the fundamental understanding of the wood-resin interaction, by looking at the relationship between the resin wetting onto wood and the resulting penetration into wood lumens. Wetting was analyzed with the sessile drop method, which observed the initial contact angle and change in contact angle over 35s. Penetration was measured within each individual tracheid. The Lucas-Washburn equation analyzed the wetting and penetration by calculating the penetration and comparing it to the measured penetration. Wetting of four resins was compared on 3 species, to improve the understanding of adhesive wetting behavior. This study agreed with previous research, that the non-aqueous resin exhibited favorable wetting and presumably better penetration than aqueous resins, with exception of urea-formaldehyde. Wetting and penetration of pMDI was studied on 5 wood species using the Lucas-Washburn equation. The wetting behaviors exhibited grain and species effects, which had implications on the resin availability for flake/strand-based composite products. The greater surface energy of loblolly pine most likely accounted for the significantly greater penetration of loblolly pine compared to Douglas-fir. The calculated penetration, via the Lucas-Washburn equation, exceeded the measured penetration, but it was concluded that the Lucas-Washburn equation predicted penetration reasonably well. Wetting and penetration of phenol-formaldehyde and subsequent adhesives was compared on 3 wood species using the Lucas-Washburn equation. All contact angles were unfavorable due to a skin formation. The Lucas-Washburn equation did not predict any penetration; however, penetration was observed with all systems. The findings suggest that the system was too complex for the Lucas-Washburn equation to be able to predict accurately. / Master of Science / Although the wood-based composites industry has been in operation for over a century, fundamental aspects of the wood/resin interaction- what happens when the liquid resin touches wood- remain poorly understood. An important aspect of this wood/resin interaction is penetration, which is critical to the strength and durability of wood-based composites. The two types of resins used, oil-based and water-based, were observed on a variety of wood species, Douglas-fir, loblolly pine, spotted gum, European beech and yellow-poplar. When using the oil-based resin, penetration measurements were in reasonable agreement with theoretical predictions. However, when using the water-based resins, the theory predicted no penetration which contradicted measurements- a shallow penetration was clearly observed. This means that parameters modeled by theory were in error, and this is sensible because we expect water to transfer from resin into the dry wood. Consequently, controlling parameters such as resin viscosity, resin surface tension, and wood surface energy were changing. This contributes fundamental knowledge, providing a better understanding of a critical step in the manufacture of wood-based composites, the materials most North Americans use to build their homes.