(Photo: Best Citizenships)

Schengen currently encompasses 26 nations, including 22 EU members, and almost 420 million people.

Bulgaria and Romania completed the evaluation process for joining Schengen in 2011, but the European Council has kept delaying admission for the past 11 years.

Croatia was confirmed to have fulfilled the conditions to join the Schengen area last December. It became a EU member in 2013 while Bulgaria and Romania joined the group in 2007.

On December 8 the Justice and Home Affairs Council will vote on the full participation of Bulgaria, Romania, and Croatia in the Schengen area.

They must prove that they have strong management of their borders with non-Schengen nations and a system for processing requests from asylum seekers, that they prioritize the fight against trans-border crimes, and that they are prepared to share security information.