All fundamental paper properties are basically determined by the three-dimensional distribution of the raw materials in the paper sheet.The structure of the main paper ingredients fiber, filler pigment and coating colour determines mechanical properties and penetration behaviour of liquids. The research project is focused on the development of technology that extracts the structure of fibers, filler pigments and coating colour to build a three-dimensional model of the paper sheet. In order to achieve this, the paper is either split into layers or cut into thin slices. In these layers or slices the spatial distribution of fibers, fillers and coating colour is identified using digital image analysis. In that way it is possible to reconstruct a three dimensional model of paper samples. The information about the tree dimensional paper structure is used to improve the paper production process in order to optimize paper properties, the focus is set to mechanical properties and print quality.