Central banks operate through the banking system and financial markets. This strategic choice requires central banks to have a thorough knowledge of how the financial system works, while at the same time it also puts them in a unique position to monitor ongoing developments in the financial system. This publication is a further step in the Eurosystem's continued efforts to improve our understanding of the financial system. The report also aims to serve as a reference work for researchers, policy-makers and the general public. Thus, it also seeks to share the Eurosystem's insights into euro area financial systems and is designed to make it easier for others to study financial structures in the euro area. Hopefully, both we and other policy-makers will benefit from these studies.