Donald Trump's controversial nominee for health secretary is fighting for support from senators who will ultimately decide whether to give him the job.
If he is confirmed, Robert F Kennedy Jr (RFK) — the nephew of assassinated president John F Kennedy (JFK) — will lead the US's Department of Health and Human Services.
His appointment is opposed by many in the medical community, who fear he holds views that fly in the face of life-saving treatments and proven science.
But his opposition to "big pharma" and ultra-processed foods, and his record as an environmental activist, has won him fans on both sides of politics.
And he said he would not apologise for asking "uncomfortable questions" that had "disturbed the status quo".
"We have massive health questions in this country that we must face honestly," Kennedy said.
Here are some of the key moments from the first day of his senate confirmation hearings.
RFK's insistence he is not anti-vax
In the past, Kennedy has suggested vaccines are dangerous and don't work. He's also pushed the theory, debunked by studies, that they cause autism.
"He has made it his life work to sow doubt and discourage parents from getting their kids life-saving vaccines," Democratic Senator Ron Wyden said.
"It has been lucrative for him and put him on the verge of immense power."
But Kennedy told the senate committee he was not anti-vaccine, and he believes vaccines "play a critical role in healthcare". He said all his own children had been vaccinated.
"I worked for years to raise awareness about the mercury and toxic chemicals in fish, and nobody called me anti-fish," he said.
Wyden confronted Kennedy over previous criticisms of vaccines he'd made on multiple podcasts.
Last year, he told the Lex Fridman science podcast: "There's no vaccine that is safe and effective." He told an earlier podcast he wanted to go back in time and not vaccinate his children.
"Are you lying to Congress today when you say you are pro-vaccine?" Wyden asked. "Or did you lie on all those podcasts? We have all of this on tape, by the way."
Kennedy said he had been interrupted on the more recent podcast, and did not get to complete his sentence.
"I was going to continue, for every person, every medicine has people who are sensitive to them, including vaccines, right? So, he interrupted me at that point. I've corrected it many times."
'No vax, no problem' onesies for babies
Independent senator Bernie Sanders said Kennedy's pro-vaccine comments were at odds with products for sale on the website of an organisation he set up.
The Children's Health Defense website is selling onesies for babies with slogans like "no vax, no problem" and "unvaxxed, unafraid".
Sanders put to Kennedy:
"You say you are pro-vaccine, you just want to ask some questions, and yet your organisation is making money selling a child's product to parents for 26 bucks, which cast fundamental doubt on the usefulness of vaccines.
"Can you tell us, now that you are pro-vaccine, that you're going to have your organisation take these products off the market?"
Kennedy said he had "no power over that organisation" because he had resigned from its board.
"Yeah, that was just a few months ago. You founded that. You certainly have power."
Sanders twice asked Kennedy if he was supportive of the sale of the onesies. Both times, Kennedy responded by saying: "I am supportive of vaccines."
Questions on a measles crisis in Samoa
Wyden pushed Kennedy on his visit to Samoa ahead of a measles outbreak that killed 83 people there in 2019. Kennedy's trip was funded by a vaccine critic.
Measles vaccination rates in Samoa had declined after the deaths of two babies in 2018 who were given incorrectly mixed vaccines.
"He travelled there himself to push his views and pour fuel on the fire of a measles outbreak that began due to low vaccination rates," Wyden said.
Kennedy said his trip had "nothing to do with vaccines."
"I never thought gave any public statement about vaccines," he said. "You cannot find a single Samoan who will say I didn't get a vaccine because of Bobby Kennedy."
Outbursts from the hearing room
On a couple of occasions, protesters interrupted the proceedings.
Outside, a small group of people opposed to Kennedy's confirmation was selling T-shirts with slogans like: "Make Polio Great Again."
But Kennedy had plenty of supporters in the room too, including his wife, actor Cheryl Hines. Some supporters wore baseball caps that said: "Confirm RFK Jr."
Backing Trump on abortion
Some anti-abortion campaigners have raised concerns with Kennedy's previous pro-choice statements.
Asked about his position on abortion at the hearing, he said he agreed with Donald Trump's position on the issue:
"I agree with President Trump that every abortion is a tragedy. I agree with him that we cannot be a moral nation if we have 1.2 million abortions a year. I agree with him that the states should control abortion."
Democratic Senator Maggie Hassan said Kennedy had "decided to sell out" his long-held values "in order to be given power by President Trump".
"What you're telling us, just to be clear because my time is limited, is that regardless of what you believe, regardless of what values you have, if President Trump tells you to do something, you're going to do it."
More criticisms from family
Before the hearing, Kennedy's cousin and former ambassador to Australia Caroline Kennedy wrote to senators to urge them to block his nomination.
Her son, popular online personality Jack Schlossberg, followed up by tweeting live commentary during the hearing.
He criticised Kennedy as "someone who cannot tell the truth" and a "lying sack of shit".
He called him an "antisemite" over his past claim that COVID may have been manufactured and "ethnically targeted" to spare Jews.
And he said Kennedy's suggestion Lyme disease was likely an engineered bioweapon was to "convince people you’re this guru shaman figure and get them into your cult".
The hearing before the Senate Finance Committee has concluded.
But Kennedy will face more questions from the Senate Committee on Health, Education, Labor and Pensions on Thursday.
