We use mathematical models basically to reduce huge amount of data concerning some complex system into a form that can be managed easily. Mathematical models, even over-simplified ones have proven to be very useful for our understanding of how complex systems work. In this talk the speaker will share some of his own experiences on the use of models and some applications that have been developed in the fields of Esthetic Sound Surgery, Tinnitus Management, Medical Imaging, Brain-Machine Interfacing, Medical Decision Support Systems and in Industrial Control. The talk will end with some some speculations concerning future developments. With the coming of the petabyte age and our capabilities to handle massive amounts of data are we at "the end of science", that is, science as we know it?"