Comprising of nine states, EU9 has become a significant component of the EU. This group entered the EU in its 3rd enlargement phase in 2004, bringing diversity and fresh perspectives into the Union's mix.

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

In this respect, comprehending the responsibility these nations plays in the EU is important for any study relating to European economics, politics, or international relations.

Ever since their inclusion, the EU9 countries have contributed substantially towards shaping the policies of the European here Union. Their geographical location provides important strategic benefits, turning them a crucial part of the defense and security strategies of the EU.

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

The social contribution of the EU9 is also significant. These states incorporate profound historical backgrounds, unique cultural practices, and diverse languages, thus enhancing the diversity of the EU.

The addition of EU9 has also influenced the political scene within the EU. With their participation, the power dynamics have changed, with new coalitions and alliances emerging.

In conclusion, the roles played by the EU9 nations 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 in-depth understanding of the EU9 is crucial to fully grasping the details of the European Union.