STORY: It's been 15 years since Kosovo declared independence from Serbia.
But the recent storming of a monastery has put tensions between the two back in the spotlight.
Here's a look at why they're still at odds.
Kosovo gained independence in 2008…
Almost a decade after a guerrilla uprising against repressive Serbian rule.
It’s recognized by more than 100 countries - including most western countries, like the United States.
But not Serbia.
It still sees Kosovo as part of its territory.
The majority of Kosovo’s population is ethnic Albanian.
Five percent of them are Serbs - of which 50,000 live in northern Kosovo, on the border with Serbia.
They receive benefits from Serbia's budgets - like free public health care and large pensions - and don't pay taxes to either side.
Serbia foots the bill for teachers, doctors and infrastructure projects and local Serbs are afraid they could lose those benefits if they become integrated with Kosovo.
They've shown their disdain a few ways - by refusing to pay their state energy bills - and by attacking police who try to make arrests.
From April, an already-tense situation became worse.
Serbs had boycotted elections.
So ethnic Albanian mayors took office in northern Kosovo.
A move that sparked rebukes from the U.S. and its allies.
There’s also a growing dispute over license plates.
Kosovo wants Serbs to switch their old ones that are from the pre-independence era.
Ethnic Serb mayors, local judges and hundreds of police officers have resigned over the looming switch.
That’s deepened dysfunction and lawlessness in the region.
What Serbs in Kosovo want is an association of majority-Serb municipalities with considerable autonomy.
Kosovo isn't a fan of that idea.
Pristina says that would create a mini-state in its borders along ethnic lines.
The U.S. and EU want both sides to get on board with a plan from 2022.
The idea: Belgrade would stop lobbying against Kosovo getting seats at international organizations like the United Nations.
Kosovo would commit to form an association of Serb-majority municipalities.
But talks stalled last week.
With powerful nationalist hardliners on both sides - prospects for an imminent breakthrough appear bleak.