This document highlights the role of control systems in the evolution of the Smart Grid. It includes an overview of research investigations that are needed for renewable integration, reliability, self-healing, energy efficiency, and resilience to physical and cyber attacks. These investigations are encapsulated in several loci of control including: new methodologies for transmission, distribution, and renewable energy, and storage; new roles in emerging topics such as electricity markets, demand-response, microgrids, and virtual power plants; and new solutions for efficiency, heating and cooling, and security. Together, they usher in new horizons for control, such as architecting a system of distributed systems, building interfaces to social sciences such as economics, sociology, and psychology, and providing a blueprint for critical infrastructure systems. While the emerging role of control and its implication on grid architectures have been articulated in various papers, a comprehensive discourse on the evolution of Smart Grid and the opportunities and challenges that it presents for control, ranging from generators to consumers, from planning to real-time operation, from current practice to scenarios in 2050 in the grid and all of its subsystems, has not been undertaken hitherto and is the purpose of this document. For Corporate or Institutional Access, request a custom quote for your organization at www.ieee.org/smartgridresearch