Watch Leah's report from Belfast on Wednesday
Police are hunting the people involved in three nights of riots on the streets of Northern Ireland.
They say that bricks and homemade bombs were thrown, and guns were fired.
Around 100 police officers tried to stop the violence. They've been using giant water canons to try and calm down the people causing the trouble.
This is all happening because of the historic troubles there - some people in Northern Ireland disagree over whether it should be part of the UK.
The violence has flared up now because Northern Ireland is in the middle of the marching season at the moment. This is when people take part in traditional parades in the street.
Some of the marchers think Northern Ireland should remain as part of the UK, but others reckon it should leave the UK.
Police vans at the riots
Sometimes this can lead to fighting between the two groups.
The police have managed to stop the trouble from spreading too much. But around 80 officers were injured in the first two nights of fighting.
Politicians and the police in Northern Ireland are meeting on Wednesday to talk about what's been going on, and how to stop the violence.