Ricky reports on the Obamas' visit
American President Barack Obama and his wife Michelle have met Prince William and Kate as part of their three-day state visit to the UK.
President Obama and Michelle chatted with the newly-wed Duke and Duchess of Cambridge at Buckingham Palace, where the visitors are staying.
No-one knows what they talked about but it's thought the Obamas congratulated them on their wedding last month.
They also met other royals, including the Queen and the Prince of Wales.
Later they're going to go to Downing Street to meet the Prime Minister David Cameron.
It's only the third visit by a US president to the UK in the last 100 years.
The Obamas are on a week-long tour of Europe that started in Dublin on Monday.
Car gets stuck on president's Irish trip
They left the Republic of Ireland ahead of schedule because of worries that their flight could be disrupted by ash cloud moving from a volcano erupting in Iceland.
In Ireland President Obama visited the home of his great-great-great grandfather. A car belonging to him got stuck as it tried to leave the US embassy in Ireland.
The president and his wife are due to spend three days looking around the UK.