We take a geometric perspective to study networks that come from the physical world, such as the wireless and sensor networks, as well as mobile and social networks. I will use a chronological order to review geometric algorithms we have developed for network management and analysis for the last two decades. Examples include network localization, geometric routing, distributed information storage and query, geometric optimization for motion planning and scheduling, as well as analysis of Internet topology and understanding social contagions. I will then introduce our recent work on new challenges on privacy from human trajectories and social ties, brought by pervasive IoT devices, big data, and social platforms.