Today's testimony by whistleblower Frances Haugen will likely keep Facebook in the hot seat for a while.

That's a wrap on our live coverage - thanks for joining us. You can follow updates to this story here.

Here's a recap of what happened today:

• Haugen said Facebook routinely prioritises its profits and growth over the safety of its users.
• When it comes to oversight and accountability she said "the buck stops with Mark" - referring to Mark Zuckerberg, the founder and CEO of the company.
• Several lawmakers pointed to research that suggests Facebook and Instagram worsen teenagers' body image issues and promote eating disorders.
• Committee Chairman Richard Blumenthal called the company "morally bankrupt" and said parents and bullied teens, among others, were watching their actions closely now.
• Haugen suggested Facebook was harmful to democracy and had taken away many safeguards it had in place for the 2020 election.
• Facebook directly pushed back against Haugen's testimony and the reporting on it, with top spokespeople tweeting out rebuttals as Haugen spoke to Congress.
• Haugen argued the company has a culture of insularity that leads to a lack of accountability.
• But she also said she does not support breaking up the company, which many politicians have suggested.

Today's reporting was brought to you by Ritu Prasad, Jessica Murphy, Marianna Brady, Sam Cabral, Holly Honderich, Bernd Debussman and David Molloy.

With the hearing wrapped, we've got a final rebuttal from Facebook.

The social media giant has condemned Haugen as a former employee that "worked for the company for less than two years, had no direct reports, [and] never attended a decision-point meeting".

"We don't agree with her characterisation on the many issues she testified about," the company's Director of Policy Communications Lena Pietsch wrote in a statement, pointing out that at least six times Haugen told senators that she did not work directly on the subject of their question.

The one-paragraph response ends with a call to lawmakers to work harder to regulate the internet.

"We agree on one thing; it's time to begin to create stand rules for the internet… Instead of expecting the industry to make societal decisions that belong to legislators, it is time for Congress to act."

Chelsea Bailey
Digital producer, BBC News

Image source, Getty Images

Emily Washburn identifies as "social media sober" after deleting all of her online profiles nearly a year ago.

Washburn told BBC News she created an Instagram account when she was 15 and now regrets spending her most formative years online.

"[As a teen] I really relied on having that constant access to my account as a sort of failsafe for when I was feeling particularly low about myself so that I could have people bring me back up again," she said.

Facebook’s own internal research shows, external that Instagram can fuel depression and anxiety, especially among teen girls.

Nearly 30% of teens surveyed by Facebook said the app made dissatisfaction with their bodies worse. Executives at the social media giant insist they are taking steps to protect the platform’s youngest users and that data from these surveys should not be scaled to represent all users on Instagram.

But for Washburn, deleting the apps was the first step to regaining control of her life.

“I think I wrote at one point, it was like an IV drip of poison. It just accrued a little bit every day,” she said.

"The more I've reflected on it, the more I realised that social media is designed to be addictive. It gets better at addicting people every day.”

Image source, Getty Images

Social media experts have said for years that apps may be harmful and addictive to some users.

In 2018, BBC Panorama spoke to an engineer who helped develop the "infinite scroll".

"If you don't give your brain time to catch up with your impulses," the man says, "you just keep scrolling."

Read more on how social media affects our behaviour.

• INVESTIGATION: Social media apps addict users
• VIDEO: How social media apps hook their users
• BBC FUTURE: How much time is too much time on social media?

Shayan Sardarizadeh
BBC Monitoring disinformation specialist

Image source, Getty Images

Throughout the Covid-19 pandemic and in the run-up to the US election, conspiracy movements and extremist groups used Facebook to amplify their message to as large an audience as possible, recruit new members and organise offline events.

The so-called Stop the Steal movement alleging election fraud, which included individuals involved in the 6 January Capitol riots, had a huge reach on Facebook.

BBC Monitoring’s research identified 78 Stop the Steal groups on the platform with hundreds of thousands of members just a week after the election. Of those, 60 were still accessible even a week after the attack on the Capitol.

Militia groups such as the Boogaloo Bois and major conspiracy movements like QAnon attracted hundreds of thousands of users on Facebook, and were removed only a few weeks before the US election.

Facebook was also a source of many viral misleading claims about Covid-19.

Followers of major anti-vaccination Instagram accounts increased nearly five-fold in 2020 and top anti-vaccination Facebook pages grew by 19%. The company announced it would start taking action against anti-vaccine content this year.

Critics also claim most of Facebook’s attempts at controlling the growth of misinformation and extremism are focused on English language content and more specifically, content posted in the US, as that’s where most of the pressure on its leadership comes from.

The company has repeatedly defended itself from such claims, saying it has taken extensive measures to keep its platform safe and remove violent movements.

As our North America reporter Anthony Zurcher mentioned in his earlier post, the political answer to the Facebook problem may end up being breaking the company apart.

Politicians around the world have suggested this in order to improve competition and safety of users.

But despite her critical testimony, Frances Haugen has said she opposes chopping up the social giant.

She said Facebook is aware of the harms its platform causes but "did not set out" to cause them.

The algorithms will "continue to be dangerous even if they’re broken up," she said.

Haugen also acknowledged that the company has "invested more than any other platform" on issues of safety - even if they are often unwilling to ask "basic questions".

Anthony Zurcher
BBC North America reporter, Washington DC

At last, Republicans and Democrats in Congress have something they can agree on – Facebook and the threat they believe it poses.

During Frances Haugen’s whistleblower testimony on Tuesday, senators on the left and the right expressed concern that the social media giant is too big and too powerful.

They had different examples in mind, of course. Democrat Amy Klobuchar worried that the company’s algorithms promoted the kind of extremist views that instigated the 6 January attack on the US Capitol. Republican Ted Cruz highlighted what he saw as Facebook’s censorship of conservative viewpoints.

Others focused on evidence Facebook ignored its own research that Instagram adversely affected the mental health of teenage girls.

Facebook’s best hope at this point may be that their opponents fracture apart over the best measures to address these concerns; that political gravity, in the end, reasserts itself.

Their executives have a limited amount of time to respond, however, if they want to avoid the political consensus becoming that the answer to the Facebook problem is the same one applied to Bell telephone in the 1980s – breaking the company apart.

David Molloy
Technology reporter

Earlier, Senator Dan Sullivan raised an old chestnut for social media companies - do they provide a platform for America’s rivals, such as China?

Haugen said she worked with Facebook's threat intelligence group, and "directly worked on tracking Chinese participation on the platform" as well as Iranian government espionage.

"This is definitely a thing that is happening," she said.

"I believe Facebook’s consistent understaffing of the counter-espionage information operations and counter-terrorism teams is a national security issue."

Asked if she’s saying America’s adversaries are using Facebook to push their interests at the expense of America’s, she replied:

“Yes, Facebook’s very aware that this is happening.”

And, giving senators food for thought (leading to suggestions of investigating it separately), she added: "I have strong national security concerns about how Facebook operates today."

With that, senators have ended their questioning and Frances Haugen has left the room after around four hours of testimony.

As the hearing nears its end, Senator Blumenthal says Haugen has sent a "profound message" to the nation that individuals can make a difference.

"You have crystalized, in a way, our consciousness," he said. "You have been a catalyst for change in a way we haven’t seen."

With a slight hint of emotion in his voice, Senator Blumenthal also said he believes that "other whistleblowers" are likely to come forward.

"I think you’re leading by example," she said. "You’re showing them there’s a path to make this industry more responsible and more caring about kids."

Blumenthal added that "a lot of parents are watching" what happens with Facebook.

"Since a lot of teens and ‘tweens’ will be going home tonight…to endure the bullying, to feel insecure about themselves," he said.

James Clayton
North America technology reporter, San Francisco

Image source, Getty Images

Silicon Valley is an extremely intimidating place to be a whistleblower.

Big Tech has the money to buy very expensive - and often aggressive - lawyers.

There is also a culture of secrecy in many large tech companies. That can be because companies don’t want their trade secrets to be spilled.

But it goes further than that here. It is a very brave thing to stick your head above the parapet like this.

Often companies will use Non-Disclosure Agreements (NDAs) to spook employees into staying silent.

That’s why Frances Haugen’s testimony is so important. There have been other whistleblowers before her, but the sheer scale and size of this leak is difficult for Facebook to push back on.

And of course, the criticism is so much more powerful when the whistleblower has a name - and can directly explain what she saw inside Facebook.

Despite her misgivings about her former employer, whistleblower Frances Haugen says she still has "empathy" for Facebook and CEO Mark Zuckerberg.

"I think they feel a little trapped and isolated," she told the hearing.

In the case of Instagram, she said that "there are real questions about where Instagram would have to come in and think hard about their product and what their product is about".

"I don’t think those answers are obvious. That’s why we need to collaborate.”

Instagram, she said, is about "bodies" and "lifestyles". She compared the platform negatively to "fun" TikTok and a number of other social media platforms.

In response to a question about whether Facebook was trying to mitigate the problems allegedly caused by the platforms, Haugen said that "with the set of incentives they were working with, they did the best they could".

"Unfortunately, those incentives are not sustainable and not acceptable in our society."

Chelsea Bailey
Digital producer, BBC News

Let's hear now from one of the teens affected by the technology being discussed in today's hearing.

"My generation, we were so immersed in this technology that I truly believe it's rewired our brains," says Rikki Schlott.

Schlott created an Instagram account when she was 11 and had thousands of followers by the time she was 16. Many of them were strangers or older men from around the world.

She spent her weekends scouring her town for the perfect Instagram spot and thought nothing of routinely editing her photos to cover her "teenage flaws" like acne.

“My sense of self was developing in this kind of bizarre duality between Instagram Rikki and real-life Rikki,” she said.

”Looking back, I'm missing a lot of photos of just being a kid and just being authentic and real.”

As a member of Generation Z, Schlott told the BBC she feels Instagram’s algorithm matured with her, and that the company treated her generation like “guinea pigs.”

Toward the end of high school, she said she had an epiphany and decided to take a step back from the apps.

She now encourages others to do the same.

"All of these realisations that we're having about the statistics, and the real shortcomings of these social media platforms can really be a moment for young people to take some personal control over their lives and reclaim their autonomy from these companies and from these platforms."

More now from inside the hearing room.

Republican Senator Dan Sullivan says he believes the world will look back and wonder "what the hell were we thinking?" following these latest revelations about Facebook and Instagram’s impact on kids.

While Haugen didn’t agree or disagree with Senator Sullivan’s statement, she reiterated that Facebook’s own research shows that Facebook is making children "unhappy".

"If Instagram is such a positive force, we would have seen a golden age of teenage mental health in the last 10 years," she said. "We’ve seen the opposite. We’ve seen escalating rates of suicide and depression amongst teenagers…in part driven by the social media phenomenon."

Teenagers are saying "‘I am unhappy when I use Instagram and I can’t stop’,” she added. "That’s so sad."

As we noted before, Facebook is responding live to today's congressional testimony.

In statements to BBC News, a company spokesperson addressed a few key points raised by Haugen in her testimony:

Claim: Instagram is 'toxic' for teen girls

Facebook's response: The spokesperson said that the company's leaked internal research "like external research on these issues, found teens report having both positive and negative experiences with social media".

The company also addressed its findings in a blog post, external by its head of research, Pratiti Raychoudhury.

She wrote that "many teens we heard from feel that using Instagram helps them when they are struggling with the kinds of hard moments and issues teenagers have always faced".

Claim: Facebook harms democracy

Facebook's response: The company says it did not end safeguards it had in place for the 2020 US election as Haugen has suggested.

A company spokesperson told the BBC they were "proud" of the work the company did to protect the election.

"We spent more than two years preparing for the 2020 election with massive investments, external, more than 40 teams across the company, and over 35,000 (now 40,000) people working on safety and security," they said.

They referenced "specific on-platforms signals and information from our ongoing, regular engagement with law enforcement" that continued - with adjustments - through the 6 January insurrection at the US Capitol.

Claim: Facebook prioritises profit and growth over safety

Facebook's response: "Protecting our community is more important than maximizing our profits," said the spokesperson.

They pointed out major investments the company has made in recent years to work on safety issues.

"To say we turn a blind eye to feedback ignores these investments, including the 40,000 people working on safety and security at Facebook and our investment of $13bn since 2016."

David Molloy
Technology reporter

Image source, Getty Images

Senators keep mentioning Facebook boss Mark Zuckerberg - but where is he?

Over the weekend, amid the controversies facing his company, Facebook's chief posted a video of a family sailing trip - something lawmakers have mentioned with scorn a few times already.

The reality is that Zuckerberg is rarely directly involved in dealing with controversies, usually delegating the task of writing blog posts or appearing in front of regulators to other senior staff.

For example, Facebook’s head of global safety testifying to this same panel last week. The company is big enough to have dedicated experts for almost every area.

But Zuckerberg has appeared before politicians before- though on one occasion, the Senate issued a subpoena to make sure he did, and he famously declined to do so in front of UK lawmakers.

Image source, Getty Images

A big part of Haugen's argument is that the only people who really understand Facebook's inner workings are its employees.

"Facebook has a culture that emphasises that insularity is the path forward," she told the members at the hearing earlier. "That if information is shared publicly, it will be misunderstood," she says.

If you follow Haugen's logic, this inward-looking culture is precisely why Congressional oversight of the social media giant is needed, some say.

And we're back to business in the hearing room after that short break. (Remember, you can watch live at the top of this page.)

Haugen is arguing that regulation may even make Facebook "more profitable over the long-term".

In response to questions from Democratic Senator John Hickenlooper, Haugen says "if it wasn’t as toxic, less people could quit it" - though that isn't something we can test.

Haugen also continued her comparisons between Facebook and the tobacco industry.

"Only about 10% of people who smoke ever get lung cancer,” she said. “So [at Facebook] there’s the idea that 20% of your users can be facing serious mental health issues and that’s not a problem."

Image source, Getty Images

We've been hearing from Frances Haugen all morning.

Here's what you need to know about the former Facebook employee taking centre stage today.

Who is she?

The 37-year-old unveiled herself on Sunday as the person behind a series of surprise leaks of internal Facebook documents.

Haugen told CBS News she had left Facebook earlier this year after becoming exasperated with the company.

Why?

She was a product manager on the civic integrity team until it was disbanded a month after the 2020 presidential election.

"Like, they basically said, ‘Oh good, we made it through the election...We can get rid of Civic Integrity now.’ Fast forward a couple months, we got the insurrection."

Facebook's Integrity chief has since contested this, saying it wasn't disbanded but "integrated into a larger Central Integrity team".

What did she do?

Before she left the company, Haugen copied a series of internal memos and documents.

She has shared them with the Wall Street Journal, which has been releasing the material in batches over the last three weeks - sometimes referred to as the Facebook Files.

Haugen says these documents prove the tech giant repeatedly prioritised "growth over safety".

David Molloy
Technology reporter

Much of Haugen’s testimony has been heard before.

A national TV interview, a month of news stories based on leaked documents, and her own prepared testimony all painted a picture of how this would go.

But unlike nearly any other high-profile political circus, it seems both sides of the aisle are unified - both on their praise for their witness and their views on the tech giant.

Haugen is polished and poised. She does not know the answer to everything but is sharing insights and opinions from inside a very secretive company.

And it appears to be working.

One of the last senators to quiz her before the recess was Senator Ed Markey, who called Haugen “a 21st century American hero”.

Not exactly the tough grilling faced by the heads of the tech firms when they are summoned to similar hearings.