Newsbeat went with five young people from BBC Generation 2015 to a Q&A with President Obama in London.
His message to them, and the hundreds of others listening, was intended to be inspirational.
Here are his main points.
"Our problems are man-made, therefore they can be solved by man, and man can be as big as we want."
Quoting former leader JF Kennedy, Obama’s message was to be optimistic.
He seemed to suggest that no matter how dark and upsetting the things on news are, if we pull together we can find a way forward.
"This world, for all of its travails, for all of its challenges, has never been healthier, better-educated, wealthier, more tolerant, less violent, more attentive to the rights of all people, than it is today."
Some people on social media reacted negatively to this, saying it was easy for a president to say and that a lot of people in the world were still suffering.
However Obama went on to say that he wasn’t saying there were no problems left to be solved, and that this progress was not a reason to sit back and do nothing.
"Reject the notion we’re surrounded by forces we cannot control. You’ve never had better tools to make a difference, to forge a better UK, a better Europe, a better world."
Whilst clearly a call to inspire young people, it has been read by some as a way of reassuring Eurosceptics that they don’t need to be worried about losing control if they stay in the EU.
"Your capacity to shape this world is unmatched."
Some of Obama’s answers focussed on how young people could campaign effectively to highlight issues to those in power.
He said the Black Lives Matter campaign had been successful at putting a spotlight on inequalities within the justice system in the US but warned against "yelling at people" once you already had their attention.
"If any of you begin to work on an issue that you care deeply about, don’t be disappointed if a year out things haven’t been completely solved,"
He said that progress was sometimes a long term project and that people must not give up.
"Seek out people who don’t agree with you. It will teach you to compromise. It will also help you if you get married."
This one got a laugh. He went on to say that "compromise does not mean surrendering what you believe".
"Ask yourself - how can I make the people around me do great things?"
Obama was asked about the most important skills to have as a world leader. He joked "having a thick skin" was pretty useful.