This book presents an overeview on the various aspects of multi-terminal DC (MTDC) grids. The major portion of the book is focused on the MTDC grids constructed based on the technology of the voltage-sourced converter high-voltage DC (VSC-HVDC) transmission, but some lights are also shed on the medium- and low-voltage DC networks. The applications, potentials and advantages of the MTDC grids are investigated. In particular, applications of the MTDC grids for integration of offshore wind farms are discussed and several topologies of the MTDC grids for offshore wind farms integration are reviewed and compared to each other, in terms of cost, flexibility and feasibility. Moreover, the techniques employed for modeling of MTDC grids are also presented. There are particular focus on control methodologies for MTDC grids and DC voltage control techniques, as the most crucial control task in context of MTDC grids.