Current biological research demands more and more the extensive use of sophisticated mathematical methods and computer-aided analysis of experiments and data. Mathematical analysis reveals similarities and differences in organization principles of metabolic, signaling and cellular interaction networks. This highly interdisciplinary book focuses on structural, dynamical and functional aspects of cellular systems and presents corresponding experiments and mathematical models. It may serve as an introduction for biologists, mathematicians and physicists to key questions in cellular systems which can be studied with mathematical models. Recent model approaches are presented with applications in cellular metabolism, intra- and intercellular signaling, cellular mechanics, network dynamics and pattern formation. In addition, applied issues as tumor cell growth, dynamics of the immune system and biotechnology are included. The book is based on selected peer-reviewed contributions and discussions at the "1. International MTBio workshop on function and regulation of cellular systems: experiments and models" (Dresden, June 24-30, 2001). The international competence and information network MTBio (Modeling and Theory in the Biosciences, www.mtbio.de) has been recently founded to improve communication between experimentalists and theoreticians sharing interests in the application of mathematical models.