Pope Francis has urged US President Donald Trump to be a peacemaker at their highly anticipated first meeting, and Mr Trump said he promised he wouldn't forget the pontiff's message.
Under clear blue skies, Mr Trump, who said sharp words about the Pope during the US election campaign last year, received a tribute from the Swiss Guard in a Vatican courtyard when he arrived.
He entered a small elevator taking him to the third floor of the Apostolic Palace and, after a long ceremonial walk past frescoed corridors, shook the Pope's hand at the entrance to the private study, which the frugal pontiff uses only for official occasions.
Before the door of the wood-lined elevator closed, a Vatican protocol official was heard quipping to the President that it was not "like Trump Tower in New York".
Pope Francis smiled faintly as he greeted Mr Trump outside the study and was not as outgoing as he sometimes is with visiting heads of state. Mr Trump, seeming subdued, said "it is a great honour".
Even when the two were sitting at the Pope's desk in the presence of photographers and reporters, the Pope avoided the small talk that usually occurs before the media is ushered out.
The two talked privately for about 30 minutes with translators.
Both men looked far more relaxed at the end of the private meeting, with the Pope smiling and joking with Mr Trump and his wife Melania.
Pope Francis' interpreter could be heard translating a comment to the First Lady: "What do you give him to eat?" Some thought he had suggested pizza but he actually said "potizza" - a pastry treat of Melania's home country Slovenia.
He then gave the President a small sculptured olive tree and told him through the interpreter that it symbolised peace.
"It is my desire that you become an olive tree to construct peace," the Pope said, speaking in Spanish.
Mr Trump responded: "We can use peace."
Pope Francis also gave Mr Trump a signed copy of his 2017 peace message titled Nonviolence - A Style of Politics for Peace, and a copy of his 2015 encyclical letter on the need to protect the environment from the effects of climate change.
"Well, I'll be reading them," Mr Trump said.
During his election campaign, Mr Trump described as a hoax scientific findings that human economic activity contributed to global warming. As US President, he has proposed deep cuts for the Environmental Protection Agency and the elimination of many environmental regulations.
Mr Trump gave the Pope a boxed set of five first-edition books by murdered US civil rights leader Martin Luther King.
As Mr Trump and the Pope said goodbye at the door of the study, Mr Trump told the Pope: "Thank you, thank you. I won't forget what you said."
Asked how the meeting with the Pope went, Mr Trump said: "Great. He is something. He is really good. We had a fantastic meeting."