In real-life social networks it is likely that social interaction behavior changes in continuous time. These changes can occur gradually or instantaneously. This section aims to develop quantitative methods for identifying such gradual changes (e.g., using moving window techniques) or instantaneous changes (e.g., using change-point detection algorithms) of social network behavior. These methods have been used to study changes in social interaction behavior during NASA’s famous Apollo 13 mission to the moon (“Houston, we’ve had a problem!”), among others.