Your right to permanent residence after four years in the EU.
The European Union gives the right to certain people to live in EU nations. Any person who exercises that right to live continuously in one EU state for four years is entitled to be given permanent resident status in that state.
The EU grants, to all EU citizens, the right to move freely between EU nations and to reside in any EU state for the purpose of study or work. You can read more about this on my page on the freedom of movement.
If you exercise this right to live in one EU state continuously for four years, the same EU treaty give you the right to live there permanently. It doesn't get you a passport but it does give you a lot of security. The same right is also extended to any dependant who has also satisfied the four year rule.
Now, four years continuously does not mean that you cannot leave for holidays or visits home but you cannot, for example, live in Germany for two years, spend a year in Belgium and then return to Germany for and count your previous two years.
I suspect that this is really most useful to families who wish to settle in another country or to those who have dependant who are not nationals of any EU or EEA state.