The Queen has made history today by becoming the first British monarch to visit the Republic of Ireland.
A massive security operation with thousands of police, one of the biggest the country has ever seen, is in place throughout the four-day trip.
Some Irish people aren't happy about the Queen visiting their country because of the troubled relationship Britain has had with Ireland over hundreds of years.
The Queen's visit is the first of its kind since the country's independence from the UK in 1922.
Here is the Queen meeting Irish President Mary McAleese. British and Irish leaders say they hope the visit will help continue to improve relations between the two countries.
During the first day of her visit, the Queen signed the visitors' book at the Irish president's official residence and also planted a tree in the surrounding grounds.
She then laid a wreath at the Garden of Remembrance for those who died fighting for Irish freedom from Britain.
It was a busy day - the Queen also visited Trinity College Dublin, Ireland's oldest university.
But protesters, unhappy that the Queen is visiting, were out on the streets.
Lots of police were needed to control some of the demonstrators.