In January Donald Trump will become the 45th president of the United States.
During the election campaign he made some controversial pledges - everything from building a wall on the border with Mexico to restricting abortion laws.
He might be the most powerful man in the world but he won't be able to do just anything he fancies.
There are certain limitations to his authority. So what can President Trump really achieve?
We asked Dr Gina Yannitell Reinhardt, an American political scientist originally from Louisiana, but who now works at the University of Essex.
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Donald Trump said: "I will build a great, great wall on our southern border and I will make Mexico pay for that wall."
Gina isn't convinced.
"He certainly cannot force the people of Mexico to pay for something," she says.
"If the United States is going to pay, he has to have congressional consent. And it's highly unlikely that a budget would ever pass with money for a wall in it."
Instead, she predicts that President Trump will "tell his people that the wall is no longer necessary because he's come up with something else instead".
She thinks it could be laser technology that gets tripped when someone tries to cross the border.
Gina's verdict: No wall.
Ban Muslims going to America
During the campaign, he said: "Donald J Trump is calling for a total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on."
Gina says this one is complicated. As president he will be "in control of the border patrol and immigration".
But she says: "That sort of law is incredibly controversial. It would, without a doubt, be taken to the Supreme Court and be judged unconstitutional."
She points out that even Donald Trump moved away from this idea as the campaign went on, instead calling for "extreme vetting" of Muslims entering the country.
Gina's verdict: No ban on Muslims.
Pressing the nuclear button
Barack Obama raised concerns about this, after it was rumoured that Donald Trump's team had banned him from tweeting.
"If somebody can't handle a Twitter account, they can't handle the nuclear code," President Obama said.
But Gina says the new commander-in-chief will have ultimate power.
"He will be in charge of the nuclear code. He will be capable of launching nuclear weapons," she says.
Gina's verdict: Trump would control any possible American nuclear strikes.
Restrictions on abortions
Years ago, Donald Trump said he was pro-choice.
The Republican party tends to oppose abortion and by the time he was running for president, Trump had changed his mind.
He was asked if women who have abortions should be punished.
"There has to be some form of punishment," he said.
He later backtracked, saying doctors who carry out terminations should be punished instead.
Gina points out that, at the minute, nobody could be punished because abortion isn't a crime but that could change.
"This is much more highly likely than some of his other promises," she says.
"It would have to take a Supreme Court verdict. So the way for Donald Trump [to do this] would be to appoint Supreme Court Justices that decided to reverse previous court decisions.
"It's likely that he will have at least two spaces to fill on the Supreme Court. And with the Senate in his favour, it's likely that they will confirm his choices.
"At that point all we're doing is waiting for a case to reach the court. It would take several years to be accomplished."
Gina's verdict: Pro-choice Americans should be worried.
Change international climate change laws
"We're going to cancel the Paris climate agreement and stop all payments of United States tax dollars to UN global warming programmes," Donald Trump has said.
"He can stop the payment of US tax dollars because it's his job to issue payments," says Gina.
"But he cannot just pull out of treaties because it is the job of Congress to join treaties."
If he has enough agreement in Congress, it's possible that he could change things pretty drastically.
Gina's verdict: It's possible.
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