The studies presented in this article address the challenges posed by the crisis. They explore promising avenues of research in the modelling of financial intermediation and the interaction between the real and financial spheres. The financial accelerator is the mechanism that causes financial constraints to amplify macroeconomic fluctuations. The contributions and limitations of two financial-accelerator models: Kiyotaki and Moore (1997) and Bernanke, Gertler, and Gilchrist (1999) are emphasized here. The financial crisis offers an incentive to transcend the two founding models, for it confronts the modeller with several challenges. Recent contributions seek to explain the banks' choice of balance-sheet structure and its impact on financial and macroeconomic fluctuations. When financial stability and inflation stability are the responsibility of the central bank alone, the MEGIS models make it possible to analyze the effects of the use of an augmented Taylor rule, the implementation of unconventional monetary policies, and crisis-exit strategies.