For example, wood cell walls absorb and desorb water depending on ambient conditions, which cause swelling and shrinking in wood that can lead to warping [7], splits [7], and wood-adhesive bonding failures [8]. However, the understanding of the swelling and shrinking in the cellular structure of wood, such as how much the cell wall material itself swells, how lumina volumes change in intact wood, and the dynamic swelling in real-time, is an active area of research in need of improved experimental approaches for adequate study [9]. Micro-X-ray computed tomography (\(\upmu\)XCT) has been established as a valuable tool to make static observations in the cellular structure in intact wood specimens. Recent advancements at synchrotrons also show promise for utilizing \(\upmu\)XCT in the study of in situ dynamic processes [11]. In \(\upmu\)XCT, X-rays are used to illuminate a specimen volume and two-dimensional projection images of the specimen are acquired as the specimen is rotated. These images are then used to reconstruct the object's three-dimensional internal structure by employing tomographic image reconstruction [12]. Select \(\upmu\)XCT examples in wood research include moisture swelling and shrinking [13; 14], adhesive penetration [15; 16], identifying axial gas permeability pathways [17], deformations during tensile adhesive lap-shear specimens [18; 19], deformations during three-point bending tests [20], and deformations caused by uniaxial compression [21]. Figure 1: Illustration of softwood cellular structure. Softwood is an anisotropic cellular material defined by the radial, tangential, and longitudinal directions [10]. It is mainly composed of longitudinal tracheids and ray cells. Pits are small openings between cells that facilitate intercellular water transport. A single longitudinal tracheid can be thought of as a hollow tube with the open space called a lumen. The cell wall is a multilamellar structure with secondary cell wall layers that are nanofiber-reinforced composites consisting of helically wound cellulose microfibrils embedded in a matrix of amorphous cellulose, hemicelluloses, and lignin [6]. Wood polymers are hygroscopic, and as a hygroscopic material wood’s properties and performance depend on the amount of water in the wood [7]. Growth rings consist of earlywood and latewood layers. Latewood is denser than earlywood because its tracheids have smaller lumina and thicker cell walls. Analyses of three-dimensional \(\mu\)XCT volumes often involve separating different classes of materials to visualize individual structures and quantify their volumes. A \(\mu\)XCT volume consists of a three-dimensional array of voxels in which each voxel has an intensity value. Segmentation is a method to separate the voxels into different object classes corresponding to different materials. When the intensity contrast between different object classes is sufficient, then the \(\mu\)XCT volume presents a multimodal intensity histogram. In such a volume, segmentation is readily achieved through traditional histogram thresholding techniques [22]. Histogram-based thresholding has been successfully utilized to visualize and quantify wood adhesive flow into wood [15; 16; 18; 19], study swelling and shrinking of wood cell walls [13], and create models to simulate axial permeability [17]. However, previous \(\mu\)XCT studies in wood have primarily focused on capturing images of static specimens. High-speed, time-resolved \(\mu\)XCT is now realized at brilliant synchrotron light sources and can be used for real-time in situ \(\mu\)XCT observations [11]. These new capabilities will enable new innovative experiments to capture in situ dynamic processes at the cellular length scale in wood and forest products, such as in situ real-time observations of mechanical deformations, pressure and temperature changes, pyrolysis, chemical modifications like biorefinery pretreatments, and transport of water and other chemicals into and out of wood.