The Queen and Prince Philip are making history with a two-day Diamond Jubilee visit to Northern Ireland.
She will be shaking the hand of Martin McGuinness, Northern Ireland's Deputy First Minister, on Wednesday.
Mr McGuinness used to be a leader in the IRA but he left the organisation after Northern Ireland's peace process began in 1998.
The royal tour is a major security operation, and for the first time in 20 visits, The Queen will stay overnight.
Politicians say this shows just how much Northern Ireland has changed.
A visit like this would have been "unthinkable" a few years ago, said Owen Paterson, the Government's Northern Ireland Secretary.
Thousands lined the streets
The Queen and her husband The Duke of Edinburgh began the tour by attending a church service in Enniskillen, to mark 60 years of the Queen's reign.
Thousands of people lined the streets, cheering and waving flags to welcome the royal couple.
The Queen later met relatives of the victims of an IRA bombing which had taken place in Enniskillen 25 years ago.
Some protests, by those who don't want Northern Ireland to be part of the UK, had been expected.
But an anti-royal demonstration in Belfast at the weekend only attracted about 300 people.