Wood bas a structure in which there are multiple regularities, sometimes similar to diffraction gratings. For instance when observing softwood in a transverse view, a bidimensional structure formed by wood tracheids appears. This structure is not homogeneus because of the decreasing size of tracheids near the limit of growth rings, and the eventual existence of other elements Iike resin canals. In radial view other structures appear, when tracheids intersect wood rays. The intrinsic variability of biological materials reduces the regularities to small zones. These types of structure allow the use of optical methods to determine the sizes of the distinguishable elements. Diffraction patterns are formed when laser light strikes a thin film of wood. From these patterns information about the structure of wood is obtained. Laser light is specially suitable for this purpose because of its high monochromaticity, directivity and power. The facts mentioned above are the basis of some devices which allow interesting measurements to be made. For example it would be possible to automate the determination of ring-width, that contains climatic information.