On 1 December 2009, the Treaty of Lisbon entered into force.

It was signed two years earlier by the leaders of the 27 member states of the European Union.

Many of the changes to the EU over the past decade have their roots in the Lisbon Treaty. In particular, the roles of the European Council and the Council of the EU were transformed, bringing concrete benefits to the work of the Union and to its citizens.

What do you know about the Lisbon Treaty? Take this short quiz.