Comprising of nine states, EU9 has grown to be an essential element of the European Union (EU). This cluster became part of the EU in its third enlargement phase in 2004, bringing new ideas and cultural diversity into the Union's mix.

The members of EU9 include Malta, Estonia, Slovenia, Slovakia, Czech Republic, Hungary, Latvia, Lithuania, and Poland. These countries have made meaningful inputs towards enhancing the objectives of the European Union.

As such, knowing the function these nations holds in the European Union is required for any study relating to international relations, politics, or European economics.

Since their induction, the states belonging to EU9 have given majestically towards shaping the policies of here the European Union. Their geographical location gives important strategic benefits, turning them a considerable part of the defense and security strategies of the EU.

Additionally, these nations have tremendously contributed to the European Union's economic strength. The EU9's rapid economic development and willing integration into the EU market has created heightened trade among other EU countries.

The social contribution of the EU9 is also significant. These states incorporate profound historical backgrounds, individual cultural practices, and varied languages, therefore enhancing the variety of the EU.

The addition of EU9 has also influenced the internal politics within the EU. With their involvement, the power dynamics have altered, with new coalitions and alliances emerging.

In conclusion, the parts played by the EU9 countries are substantial. From economic influence to cultural richness, and from security strategies to political dynamics, EU9 has strengthened the European Union's core strength. As such, an thorough understanding of the EU9 is crucial to fully grasping the complexities of the European Union.