The last decade has been a decennium horribile for the EU. Since 2008, the European Union has faced a series of unprecedented shocks: the Great Recession, the sovereign debt crisis and its dramatic social consequences, security threats linked to terrorism and conflicts in the MENA region (Middle East and North Africa), the refugee crisis and, eventually, Brexit. Supranational decision making was severely tested. Against all odds, however, the destructive spiral stopped short of driving the Union into self-destruction: a circumstance that still calls for an explanation. Only a thorough retrospective analysis of the political crisis can cast light on the nature of this unexpected resilience. SOLID is the result of the synergies which brought together prof. Maurizio Ferrera, Professor of Political Science at Università degli Studi di Milano, Hanspeter Kriesi, Professor of Political Science at the European University Institute and Prof. Waltraud Schelkle, formerly Professor in Political Economy at the London School of Economics and currently Joint Chair for European Public Policy at the Robert Schuman Centre for Advanced Studies of the European University Institute.