This lecture by the instructor covers the fundamental structures of dynamic communication networks, exploring topics such as limits of predictability in human mobility, network communities, and community detection in networks. It delves into the definition and identification of communities in networks, both in strong and weak senses, and discusses the importance of link communities in revealing multiscale complexity in networks. The presentation also touches on the anatomy of meetings, social interactions throughout the day, and the implications of null models in understanding dynamic social networks.