Social network analysis has become an important tool in studying social phenomena. An issue often addressed is how the structure of a network affects the actors comprising it; for instance, how is the behavior of actors influenced by the behavior of (particular) other actors in the network? An issue less commonly explored deals with how actors shape their networks; for instance, on the basis of what attributes do organizations choose other organizations as partners? In addition, these two issues are interdependent; for instance, friends are often chosen on the basis of similarity of behavior and interests, but, at the same time, friendship makes friends more similar. Theoretical models for changes in behavior and/or network structure exist, but statistical models for actual testing and forecasting are largely lacking. This book provides such statistical models, with the help of which it is possible to answer a range of questions concerning the dynamics in networks, including the questions raised above.