Questions over how border between Northern Ireland and Republic will be controlled
Will Brexit threaten fragile ceasefire?
Britain’s Out vote could see the introduction of border controls between Ireland and Northern Ireland.
With uncertainty over what happens next there are fresh concerns about the relationship between the North and South.
Some have suggested a “hard border” to control movement of people and goods between the territories.
This could involve a passport checkpoint or electronic checks.
Prior to the vote both the UK and Northern Ireland were part of the EU, and there was unrestricted free movement across the border.
An important part of the Irish peace settlement was a deal to make the border less important.
It is feared the referendum result will put the fragile 1994 ceasefires at risk.
But following Brexit, Sinn Fein has made calls for a border poll.
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Declan Kearney, of the Northern Ireland Assembly, told the BBC: "This outcome tonight dramatically changes the political landscape here in the north of Ireland and we will be intensifying our case for the calling of a border poll.”
Enda Kenny, leader of Fine Gael and Taoiseach, warned throughout the campaign that we could see a return of border controls.
Today the Irish government has said the UK vote to leave the European Union will have "very significant implications for Ireland".
Northern Ireland voted to remain in the EU Referendum by a majority of 56% to 44%.
But the UK voted by a narrow margin to leave.
Only London and Scotland backed up its Remain stance.
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