The euro has been in use since 1999 as a non-cash accounting unit and since 2002 as physical currency. Today, it is the official currency in 20 countries. Despite its wide circulation, the euro still hides a number of intriguing details.

Here are five curious facts about the euro you may not know ? from the design of its banknotes to the materials they?re made from.

1. The ?2 coin commemorates 388 historical events

What do Asterix, the discovery of Antarctica, and Park Gell have in common? All three ? along with 385 other anniversaries, figures, and events ? have been honored by the EU through commemorative ?2 coins. Each member state can issue up to two commemorative ?2 coins per year. Greece was the first to do so, marking the 2004 Athens Olympic Games.

2. The euro plays a key role in fighting climate change

Both the European Union and the eurozone lead globally in issuing ?green bonds? ? financial instruments used to fund projects that benefit the environment and climate.

In 2020, 49% of all green bonds worldwide were issued in euros, and 51% were issued by EU institutions.

3. Euro banknotes are made from cotton

Euro banknote paper is primarily produced from cotton fibers ? specifically ?cotton noils,? a by-product of the textile industry.

In 2019, approximately 5,210 tons of cotton fibers were used to produce euro banknotes, with 57% sourced from certified sustainable origins. The long-term goal is for all euro banknotes to be made from sustainable cotton.

4. Which banknote is used the most?

The first series of euro banknotes, introduced in 2002, featured seven denominations: ?5, ?10, ?20, ?50, ?100, ?200 and ?500.

These have gradually been replaced by the second ?Europa? series. The most widely used banknote today is the ?50 note ? with 13.6 billion pieces currently in circulation, according to BusinessNovinite.