This book, unlike other books, provides readers with a practical yet sophisticated grasp of the macroeconomic principles necessary to understand a monetary union. By definition, a monetary union is a group of countries that share a common currency. The most important case in point is the Euro area. Policy makers are the central bank, national governments, and national labour unions. Policy targets are price stability and full employment. Policy makers follow cold-turkey or gradualist strategies. Policy decisions are taken sequentially or simultaneously. The countries can differ in size or behaviour. Policy expectations are adaptive or rational. To illustrate all of this there are numerical simulations of monetary policy, fiscal policy, and wage policy.