The transformation of modern electricity grids at the local and global scale into smart grids is at the core of sustainable economic, environmental and societal growth worldwide. This migration to more intelligent, user-friendly and responsive grids around the world is in large part enabled by the development and deployment of appropriate communication and information technologies. Such Smart Grid Communication systems need to be seen as part of a larger system of systems to manage energy generation and distribution with C3 technologies - Communication, Control and Computing - playing key roles. Smart Grid Communications support such applications as control and information processing systems to support two-way energy flows, the automatic management of power outages, and the integration of renewable energy sources and allowing the consumers to play an active role in energy production and adaptive consumption. The resulting rich confluence of disciplines is part of the specific challenge and appeal of smart grid communications research and development.