Facebook is facing a historic crisis.

Revelations brought to light from whistleblower Frances Haugen, a former data scientist at Facebook, has led to what may be the most threatening scandal in the company's history.

The pressure was turned up on Tuesday, when Haugen testified before a Senate subcommittee. She provided a clear and detailed glimpse inside the notoriously secretive tech giant. She said Facebook harms children, sows division and undermines democracy in pursuit of breakneck growth and "astronomical profits."

Past controversies over Facebook's role in Russian attempts to influence the 2016 election and the social network's lax handling of user data in the Cambridge Analytica case were crises that rocked the company and spurred internal reform.

But the fury that Haugen's revelations have set off is different. Here are four reasons why.

Haugen was an insider, making her a powerful critic

Haugen worked at Facebook for nearly two years after stints at Google, Yelp and Pinterest.

At Facebook, she studied how the social network's algorithm amplified misinformation and was exploited by foreign adversaries.

Haugen told Congress that Facebook consistently chose to maximize its growth rather than implement safeguards on its platforms, just as it hid from the public and government officials internal research that illuminated the harms of Facebook products.

"The result has been more division, more harm, more lies, more threats and more combat. In some cases, this dangerous online talk has led to actual
violence that harms and even kills people," Haugen testified.

Before Haugen left the social network, she copied thousands of pages of confidential documents and shared them with lawmakers, regulators and The Wall Street Journal, which published a series of reports called the Facebook Files.

"During my time at Facebook, I came to realize a devastating truth: Almost no one outside of Facebook knows what happens inside Facebook," Haugen told Congress. "The company intentionally hides vital information from the public, from the U.S. government, and from governments around the world."

Haugen is not the first ex-Facebook employee who has raised concerns about the world's largest social network. But two things distinguish her: She is a compelling witness, speaking with conviction, specificity and depth. And she came armed with receipts to buttress her account — the thousands of pages of company documents that lay bare exactly what Facebook knew about its products.

Facebook executive Monika Bickert told NPR's Morning Edition that the company does not place profits over safety, citing the social network's halting of political ads before the November presidential election.

In a lengthy blog posted Tuesday evening, Facebook CEO Mark Zuckerberg said that company's internal research has been misrepresented.

"It's disheartening to see that work taken out of context and used to construct a false narrative that we don't care," Zuckerberg wrote.

He said he is "particularly focused" on the questions raised about how Facebook products affect children, writing that "it's very important to me that everything we build is safe and good for kids."

Research shows Facebook coveted young users, despite health concerns

Of particular concern to lawmakers on Tuesday was the impact on children by Instagram, which is owned by Facebook.

Haugen has leaked one Facebook study that found that 13.5% of U.K. teen girls in one survey say their suicidal thoughts became more frequent after starting on Instagram.

Another leaked study found 17% of teen girls say their eating disorders got worse after using Instagram.

About 32% of teen girls said that when they felt bad about their bodies, Instagram made them feel worse, Facebook's researchers found, which was first reported by the Journal.

Sen. Marsha Blackburn, R-Tenn., accused Facebook of intentionally targeting children under age 13 with an "addictive" product — despite the app requiring users be 13 years or older.

"It is clear that Facebook prioritizes profit over the well-being of children and all users," she said.

Subcommittee Chair Richard Blumenthal, D-Conn., echoed this concern.

"Facebook exploited teens using powerful algorithms that amplified their insecurities," Blumenthal said. "I hope we will discuss as to whether there is such a thing as a safe algorithm."

Haugen told Congress that when outside researchers and lawmakers asked how Facebook affected the health and safety of children, the company was never forthcoming.

"Facebook chooses to mislead and misdirect. Facebook has not earned our blind faith," Haugen told Congress.

Facebook has responded that other internal research shows that young people who use Instagram feel more connected to their peers and better about their well-being.

After the Journal's reporting, Facebook said it was pausing work on an Instagram product tailored to kids under the age of 13.

Democrats and Republicans are actually united on regulating Facebook

At one moment in the hearing, Republican Sen. Jerry Moran of Kansas turned to Blumenthal and said they should put aside their partisan differences to tackle a common goal: reining in Facebook.

On such regulation, Blumenthal said: "Our differences are very minor."

"I share that view," Moran replied.

Later, during a press conference, Blumenthal referenced the bipartisan unity at the hearing.

"If you closed your eyes, you wouldn't know if it was a Republican or a Democrat," he said. "Every part of the country has the harms that are inflicted by Facebook and Instagram."

But what might lawmakers do about those harms?

Haugen urged lawmakers to examine the algorithms that drive popular features, like the main feeds in Facebook and Instagram.

The algorithms reward engagement. In other words, when a post receives comments, "likes" and other interactions, it is spread more widely and is featured more prominently in feeds, instead of just featuring posts in chronological order. The engagement-based formula helps sensational content, such as posts that feature rage, hate or misinformation, travel far and wide, she said.

"It is causing teenagers to be exposed to more anorexia content. It is pulling families apart. And in places like Ethiopia, it's literally fanning ethnic violence," Haugen told lawmakers. She added that reforms should make "the platforms themselves safer, less twitchy, less reactive, less viral."

One proposal now being discussed by Blumenthal would let private citizens sue Facebook and other social media companies for harm caused by their algorithms.

Right now, a decades-old law known as Section 230 immunizes social media companies from being sued over what their users post, but lawmakers are examining possible carve-outs.

"I would see curtailing that legal shield and immunity so as to give victims and survivors of harms that occur as a result of content on the Internet some recourse," said Blumenthal at a briefing after the hearing.

Other legislative responses could include passing a national privacy law and strengthening safeguards for children online, two measures that have been long-debated among Washington lawmakers. But lawmakers insist Haugen's disclosures are the motivation needed on Capitol Hill.

Haugen stood against breaking up Facebook, a popular rallying cry in Washington. She said it would only worsen the platform's problems by turning the social network into a Frankenstein monster that would still causes harm around the world, while a separate Instagram would siphon most of the advertising dollars.

Haugen says Facebook broke the law

Haugen's lawyers have filed eight complaints with the Securities and Exchange Commission focused on Facebook's public statements about issues including what Facebook knew about how organizers of the Jan. 6 Capitol siege used its platform; how effective it is as removing hate speech; and how Instagram makes body image issues worse.

According to Haugen's legal team, Facebook executives, including CEO Mark Zuckerberg, misstated and omitted key details about what was known about Facebook and Instagram's ability to cause harm.

Attorneys for Haugen allege that Facebook violated U.S. securities laws by lying to investors.

The documents were also shared with state prosecutors, including the California attorney general, Haugen's lawyer, John Tye, told NPR.

Federal regulators and state prosecutors have not indicated how authorities plan to respond.

Facebook is turning up the heat on Haugen, suggesting for the first time that she broke the law. Company executive Monika Bickert told CNN on Tuesday that the documents Haugen obtained were "stolen."

Federal whistleblower protections provide legal cover to Haugen in providing private Facebook documents to the SEC and Congress, but experts say her leaks to the press could trigger legal action from Facebook.

Editor's note: Facebook is among NPR's financial supporters.