South Korea's Ban Ki Moon has taken over as secretary general of the United Nations - the first Asian to hold the post in 35 years.
The South Korean former foreign minister is the organisation's eighth leader and succeeds Kofi Annan, who was at the helm for 10 years.
Mr Ban faces a number of global crises as well as reform of the UN itself.
He has vowed to be a bridge-builder and a harmoniser and to set the highest ethical standards.
The BBC's UN correspondent in New York, Laura Trevelyan, says Mr Ban, 62, has given little away about his diplomatic priorities.
More to read in the BBC article.