Germany is a country that used to be ethnically pretty homogeneous but which is now becoming much less so. The change in Germany's ethnic makeup has been the cause of a fair amount of tension within the country.
According to the CIA Factbook (link below) Germany is 91.5% German. This is a large percentage, of course, but Germany's Turkish and Muslim population is growing rapidly. Turks currently make up 2.4% of the population of Germany and Muslims make up 3.7%.
The fact that there is a relatively large population of people with a different ethnicity and religion has caused problems. Germany is currently struggling to figure out how to integrate ethnic Turks into the German population. Up to this point, they have been largely excluded, but they are becoming a bigger portion of the society and Germans are starting to feel that they must be assimilated.