A customer pays with euro in cash at a store in Brussels, Belgium, Dec. 28, 2018. On the eve of the euro's 20th anniversary, European Union leaders lavished praise on the common currency on Monday, calling it "one of the biggest European success stories." On Jan. 1, 1999, 11 EU countries launched the euro and introduced a shared monetary policy under the European Central Bank. It is now the currency of 340 million Europeans in 19 EU member states. (Xinhua/Zheng Huansong)