A network is a collection of objects interacting with each other. Networks are found in numerous scientific disciplines: atoms or interacting particles in statistical physics, protein interactions in molecular biology, social networks in sociology and the Internet web-graph in computer science, just to name a few. Several types of interactions exist. While binary interactions are the simplest (did Alice interact with Bob today?), weighted interactions (the number of interactions between Alice and Bob today) or temporal interactions (at what precise times did Alice and Bob interact?) provide additional valuable information.