I think (almost) everyone has heard or used the Euro. The single European currency in 13 countries, the Euro - in my opinion - changed Europe.
The Euro was already introduced as an accounting currency in 1999, but only took physical shape in 2002. Most EU countries joined in using the Euro, notably though the UK, Denmark and Sweden still do not use the Euro.
The currency consists of coins and notes.
The coins are of 2euro, 1 euro, 50cents, 20cents, 10cents, 5cents, 2cents, and 1cent. Interesting about the coins is that one side is identical to all countries using the Euro, the other representing a 'national' symbol. Trust me some coins have become real collectors items.
The notes are of 500euro, 200euro, 100euro, 50euro, 20euro, 10euro and 5euro and are all the same throughout the countries using the Euro. The design on the notes represents different European architectural styles.
The statue in the photo is Europa, holding the Euro and is situated in front of the European Parliament.
I would call this EU lesson no. 2.