Interaction networks are a convenient way of representing the complex nature of multi-component systems. Examples of such complex systems include biological pathways, social interactions, financial markets, management systems, multiple modules in a programming language, etc. Recent emergence of systems biology has brought biological networks into focus. Such biological networks can be of various types, ranging from protein-protein interactions, gene regulatory networks, metabolic networks, microbe co-occurrence and co-inhibitory networks, etc., and can be investigated using appropriate network analysis methods. This section deals with different types of tools to analyse and compare multiple biological networks.