Microgrid is a promising paradigm for the large scale integration of DER in distribution networks. This paper addresses the state of the art in the conception, operation and design of microgrids. It also discusses the impact and contributions to distribution grids of multiple microgrids, coordinated through an aggregator agent. Microgrids may operate as isolated electrical systems in case of contingency in the distribution network; a comprehensive analysis on the energy management system and stabilizing control for such operation mode, as well as for the grid connected mode, is provided. This paper reflects the vision of the Catalonia Institute for Energy Research (IREC) for near future microgrids based on the experience of its laboratory test bed.