![Various denominations of the euro.](/sites/default/files/styles/large/public/Euro_banknotes.png?itok=AfKKrNR6)
Various denominations of the euro, which replaced national currencies in most EU member nations
![EU Parliament Building.](/sites/default/files/styles/large/public/800px-Institutions_europeennes_IMG_4300.jpg?itok=BmOfM1gB)
The EU Parliament meets in Strasbourg, France.
![Signatories of the Treaty of Lisbon.](/sites/default/files/styles/large/public/Tratado_de_Lisboa_13_12_2007_%28081%29.jpg?itok=X56JWH7M)
The Treaty of Lisbon, whose signatories are pictured here, was adopted by the EU in 2009 after years of torturous debate, public resistance, and revision.
![The European Central Bank in Frankfurt.](/sites/default/files/styles/large/public/Frankfurt_Eurotower.20130603.jpg?itok=m-RKGtGE)
The European Central Bank in Frankfurt, Germany, governs EU monetary policy.
![2003 German stamp commemorating the Maastricht Treaty.](/sites/default/files/styles/large/public/Stamp_Germany_2003_MiNr2373_Vertrag_von_Maastricht.jpg?itok=qYbXGX9X)
This 2003 German stamp commemorates the 10th anniversary of the Maastricht Treaty.
![Public opinion on EU initiatives.](/sites/default/files/styles/large/public/800px-Oui_Non_Non_Bourgogne_2005.jpg?itok=zBNaoNtc)
These political posters reflect divided public opinion on EU governance. French voters rejected a European Constitution in 2005, and the draft constitution was later replaced by the Treaty of Lisbon.
![The signing ceremony for the Treaty of Rome.](/sites/default/files/styles/large/public/Treaty_of_Rome.jpg?itok=mWeSZxVg)
The signing ceremony for the Treaty of Rome in 1957, establishing the European Economic Community
![100,000 Greek citizens protest austerity measures.](/sites/default/files/styles/large/public/2011_Greece_Uprising.jpg?itok=aGc4_Nyp)
100,000 Greek citizens protest austerity measures in front of the Parliament building in Athens, 2011.
![Jean Monnet on the cover of Time.](/sites/default/files/styles/large/public/1101611006_400.jpg?itok=cYGYdJAx)
Jean Monnet, the French businessman considered by many to be the founding father of the EU
![Robert Schuman.](/sites/default/files/styles/large/public/220px-Robert_Schuman.jpg?itok=POv9ITKF)
Robert Schuman, a German-French statesman who helped articulate the goals of uniting Europe
![EU Commission President José Manuel Barroso.](/sites/default/files/styles/large/public/Jose_Manuel_Barroso%2C_EU-kommissionens_ordforande%2C_under_ett_mote_i_Folketinget_2006-05-19_%281%29.jpg?itok=0TBKfalF)
EU Commission President José Manuel Barroso had promised to “defend the euro, whatever it takes.”
![Croatian and EU flags.](/sites/default/files/styles/large/public/800px-Croatia_EU_flags.jpg?itok=zVFH3mjc)
Croatia recently joined the EU. Its flag hand here to the right of the EU flag.