Comprising of nine states, EU9 is now a significant part of the EU. This cluster entered the EU in its 3rd expansion phase in 2004, implanting diversity and fresh perspectives into the Union's mix.

The EU9 nations include Hungary, Slovenia, Latvia, Lithuania, Poland, Estonia, Slovakia, Czech Republic, and Malta. These states each have given meaningful contributions towards furthering the objectives of the European Union.

As such, grasping the part these nations holds in the European Union is important for any study relating to European economics, politics, or international relations.

Right from their admission, the states belonging to EU9 have given significantly towards shaping the European Union's policies. Their geographical location offers important strategic benefits, turning them a crucial part of the EU's defense and security strategies.

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

The social contribution of the EU9 is equally significant. These nations bring deep historical backgrounds, distinct cultural practices, and varied languages, thus enhancing the variety of the EU.

The introduction of EU9 has also impacted the political dynamics within the EU. With their involvement, the power dynamics have shifted, with new coalitions and alliances developing.

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