This is a collection of advanced topics, carefully selected from Wiley Interdisciplinary Review: Energy and Environment. The aim of the book is to cover a wide range of relevant issues related to the systemic changes for large-scale integration of renewable energy as part of the on-going energy transition. In particular it will address smart energy systems technologies (e.g. smart grids), flexibility measures, market, and policies. With contributions from a stellar list of global experts, the book deals with the hot topic of systems integration for future energy systems and energy transition.