After the collapse of Communism in 1990, the European Union (EU) has immediately sustained in the process of democratization in the ex-communists countries, and has provided necessary technical and financial assistance in order to place a market economy. The enlargement was (and always is) the most significant and the most ambitious European project since the signature of the Treaty of Rome: it reconciles one of the economic projects of the united Europe with geo-strategic vision of the European continent, which will allow the important position of the EU in the World. The 1st May 2004 the EU has passed to the twenty-five member countries, with accession of ten New Member States (NMS). The process of enlargement has continued on January the 1st, 2007 by accessing to the EU of Bulgaria and Romania. The Single Market”, Economic and Monetary Union (EMU) and the process of integration are the major points of the Europe of twenty-seven member countries. The process of preparation of accession to the EU, has announced the preparation in the Central and East European Countries (CEEC) from the 1989, and it marked some difficulties for the CEEC – on the level of political integration but also economic and social. The present article show us, also, the importance of the introduction of the euro – which present the very important phase in the evolution of the EU, and the biggest monetary changement in the history of Europe…We consider euro as the concretization of the EU. It represents the success of the “Single Market” and contributes to the economic stability of the EU. Also, it is important to know that the euros play his important role to the politic and economic fields. The New Member States (NMS) are engaged to enter to the EMU in his future. For the success of their entrance to the EMU, the NMS have to align their economies with these of the old member states of the EU. This economic alignment, so called “convergence”, constitutes the supplementary phase on their aim toward European integration. The latest enlargements represent the most important moments in the history of the European continent. Today, the question is also the integration of the Balkan countries to the EU and their future toward European integration.