The 1998 Good Friday Agreement brought peace to Northern Ireland.
But the issues that divided the region haven't gone away.
And now, in the aftermath of the UK's departure from the EU - the situation has got worse and threatens to derail that agreement.
Pro-British loyalists say, the post-Brexit trade agreements threaten Northern Ireland's place in the UK, while Irish nationalists accuse them of using the issue to stoke trouble.
Dozes of police officers have been hurt in a week of riots, prompting regional and international governments to appeal for calm.
So, can the tension be contained?
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