The current networking scenario is characterized by widespread availability of ubiquitous devices with significant processing capabilities, e.g., smartphones, tablets, and laptops. In addition, the simultaneous availability of multiple connectivity interfaces, e.g., cellular, WiFi, and Ethernet, pushes towards spontaneous networking scenarios where devices create a multinetwork environment based on collaborative and best-effort dispatching of packets. Connectivity in such novel scenarios is far less reliable than in traditional networks, e.g., links abruptly dis/appear simply due to node mobility, thus making hard to support quality-sensitive applications. In this book, we present our middleware for Tree-based Overlay over Multiple and Heterogeneous spontaneous networks for easily supporting smart network management features on top of heterogeneous multinetwork environments. It creates and maintains a dynamic and mobility-aware tree-based overlay network to integrate different connectivity technologies while enabling a tradeoff between accuracy of the global network view and collection/monitoring overhead.