Wetting Phenomenon of Fibrous Structures: Test Methods and Mathematical Modelling of the System. Experiments are inevitable in order to collect required information about the investigated target. Unfortunately in most of the cases it is time consuming and usually additional auxiliary appliances are needed. For the investigation of the processes that are being performed in a macroscopic or in a microscopic levels, nowadays used test methods may not be a sufficient tool. Analysis for this type of processes can be simplified by implementation of mathematical modeling. It can also save time, visualize the process and deliver reliable results.