Biological processes form large, complex networks of interacting molecules that fulfill various vital tasks in living organisms. Sophisticated bioinformatics methods are required to process, organize, search, combine, analyze, and visualize the enormous amounts of heterogeneous biological information contained in experimentally and computationally derived interaction data. In particular, different types of molecular networks are intertwined in each cell, and many of them involve proteins. The talk will focus on the importance of interacting protein regions for the functional and structural analysis of protein networks that may be disturbed in diseases.