This chapter discusses time-varying network models, which allow for network models with parameters that change across time. These models are relevant when one is interested in how individuals change across time. The chapter introduces the reader to time-varying models and discusses various methods to estimate them, which make different assumptions about the true time-varying nature of parameters. Finally, the chapter illustrates one of the methods by fitting a time-varying Gaussian graphical model (GGM) to a time series of mood related measurements.