This dissertation consists of two chapters on macroeconomics with financial frictions. The first chapter studies the role of firm heterogeneity in the transmission of financial shocks to the real economy. Evidence from the recent European debt crisis shows that firms responded differently to the severe credit tightening that occurred during this period, where smaller ones adjusted their balance sheets more aggressively and performed better in economies with a more skewed firm size distribution. A model of heterogeneous firms, that face financial frictions (defaultable debt and costly equity issuance), a financial intermediation sector, and a sovereign, is proposed to explain these facts. Financial frictions are key because they generate fin...