This book assembles current theoretical contributions to monetary theory, banking and finance. The papers published in this collection span a wide variety of themes, from monetary policy to the optimal design of financial systems, from the study of the causes of financial crises to payment systems design. Thereby, the book serves as a useful reference to all researchers interested in the study of financial systems and monetary economics. The papers contribute to two strands of literature: A first group of papers focuses on topics related to the optimality of financial mechanisms, banking regulation, financial crises, financial fragility, and payment systems. A second group of papers is broadly concerned with the efficiency of the decentralized monetary solution in economies characterized by equilibrium heterogeneity.