The European electricity sector is undergoing radical changes in every segment of the power industry, from generation to supply. Ambitious policy goals set at European level to enhance the competitiveness, security and sustainability of the EU's energy system have called for major changes in the regulatory, technological, and market structure fields. The distribution sector is particularly affected by these changes. The increasing penetration of local renewable generation and the emergence of demand response enabling solutions are placing new requirements on the distribution networks, posing challenges to the reliability and efficiency of system operation. At the same time however, these new applications can also create opportunities to manage the distribution grids in a more flexible and efficient way. Smart grid concepts and technologies have an important role to play to address these new challenges and opportunities. A variety of solutions are already being tested in Europe, with encouraging results. Identifying the best technical, economic and social options requires a deep understanding of their impact on the physical distribution networks. Such knowledge is also necessary to evaluate the viability of replicating and scaling up pilot experiences already successfully implemented in Europe. At present, there is little publicly available information on the European distribution system operators (DSOs) and the networks they operate. Such lack of knowledge is partly attributable to the DSOs' reluctance to share data that can be considered as assets of commercial value, but it is also due to the vast number and heterogeneity of the distribution systems in Europe. ...