Recent advances in quantum information science enabled the development of quantum communication network prototypes and created an opportunity to study full-stack quantum network architectures. This talk introduces SeQUeNCe, a comprehensive, customizable quantum network simulator. Our simulator consists of five modules: Hardware models, Entanglement Management protocols, Resource Management, Network Management, and Application. This modularized framework is suitable for simulation of quantum network prototypes that capture the breadth of current and future hardware technologies and protocols. We implement a comprehensive suite of network protocols and demonstrate the use of SeQUeNCe by simulating a quantum key distribution network, a teleportation network, and a metropolitan quantum network in the Chicago area consisting of nine routers equipped with quantum memories. Quantum network simulations are expected to play an increasingly important role in designing future quantum networks that scale to long distances and large number of hosts, and meet the latency, reliability and security needs of emerging applications. SeQUeNCe is freely available on GitHub.