With the mental health of teens and preteens a prime focus at Tuesday's hearing, Sen. Amy Klobuchar, D-Minn., asked Haugen directly if Facebook hooks users to its platforms at a young age in order to make them more profitable over the long term.

"They know that children bring their parents online -- so they understand the value of younger users for the long-term success of Facebook," said Haugen.

She also said they know children will bring family members to the platform, if not the reverse.

"Facebook understands that if they want to continue to grow they have to find new users. They have to make sure that the next generation is just as engaged with Instagram as the current one, and the way they'll do that, making sure children establish habits before they have good self-regulation," added Hagen.

"By hooking kids?" asked Sen. Brian Schatz, D-Hawaii.

"By hooking kids," Haugen affirmed. "We need to protect the kids."

-ABC News' Zunaira Zaki, Mary Kathryn Burke and Victor Ordonez

Lawmakers on the Senate Commerce subcommittee on Consumer Protection, Product Safety, and Data Security focused on whistleblower Frances Haugen's leaked internal documents showing the media giant found evidence of its harmful effects on young users and its fueling of misinformation but did nothing to address either, putting "profits before people."

For the effect on kids, Haugen said it's a problem previous generations did not have to face.

"Kids who are bullied on Instagram, the bullying follows them home. It follows them into their bedrooms. The last thing they see before they go to bed at night is someone being cruel to them. Or the first thing in the morning, someone being cruel to them," she said.

She added the Facebook "definitely" targets kids as young as eight years old through its Messenger platform, among other tactics.

Haugen said if she had the power, she would establish more transparency with congressional oversight bodies, propose legislation on what an effective oversight agency would look and immediately re-implement the "soft interventions" identified to protect the 2020 election.

"No one censored being forced to click on a link before resharing it," she said.

Sen. Amy Klobuchar, D-Minn., raised the alleged harmful effects of Instagram, which is owned by Facebook, and the data whistleblower Frances Haugen leaked showing Facebook's own research found that more than 13% of teenage girls said that Instagram made their thoughts of suicide worse.

"What did they do? They proposed 'Instagram for Kids,' now been put on pause, because of public pressure," Klobuchar blasted, before asking Haugen if Facebook knows data has shown Instagram also promotes eating orders in young girls.

"Facebook knows that they are leading young users to anorexia content," Haugen said.

An internal Facebook study shown to lawmakers by Haugen that Klobuchar cited said 17% of teen girls said Instagram makes eating disorders worse.

Comparing the social media giant to tobacco companies targeting youth, Haugen said that Facebook is deliberately designing their product to be addictive.

"Facebook has a long history of having a successful and very effective growth division where they take little, tiny tweaks and constantly, constantly, constantly trying to optimize is to grow," she added.

Asked whether CEO Mark Zuckerberg would be the one to dictate the decisions around Facebook's algorithm, whistleblower Frances Haugen said yes, noting his "unique" role in the company, noting he holds over 55% of all voting shares.

"There are no similarly powerful companies that are as unilaterally controlled, and in the end, the buck stops with Mark," Haugen said. "There's no one currently holding Mark accountable but himself."

In her opening statement, Haugen echoed Sen. Richard Blumenthal, D-Conn., in comparing Facebook's reckoning to a "big tobacco moment" and called on the government to take action.

"As long as Facebook is operating in the shadows, hiding its research from public scrutiny, it is unaccountable. Until the incentives change. Facebook will not change," she said.

"When we realized big tobacco is hiding the harms that it caused, the government took action. When we figured out cars were safer than seatbelts, the government took action. And when our government learned that opioids are taking lives, the government took action," she said. "I implore you to do the same here today."

Haugen said that Facebook "wants you to believe that the problems we're talking about are unsolvable. They want you to believe in false choices. They want you to believe that you must choose between a Facebook full of divisive and extreme content or losing one of the most important values."

"I'm here today to tell you that that's not true," she said.

After more than three hours of testimony, the Senate Commerce subcommittee hearing with Facebook whistleblower Frances Haugen, who has accused the company of deceiving users and investors and putting "profits before people," has adjourned.

While lawmakers battle it out over President Joe Biden’s agenda, they united on Tuesday to blast Facebook CEO Mark Zuckerburg’s silence on Haugen accusations, which raise alarms about the mental health of children and real-world dangers of hate speech she said Facebook knows it perpetuates but ignores. Lawmakers said she has provided hundreds of pages of documents of internal data to back her claims.

Sen. Richard Blumenthal, D-Conn., the subcommittee chair, closed by reading a text he said he received from a constituent who said he was in tears watching the hearing because, he said, he's seen first-hand how Instagram has changed his teenage daughter.

"'My 15-year-old daughter loved her body at 14. Was on Instagram constantly and maybe posting too much. Suddenly she started hating her body. Her body dysmorphia, now anorexia, and was in deep deep trouble before we found treatment. I fear she'll never be the same,'" Blumenthal said, quoting the father.

Haugen said "because of the nature of engagement-based ranking and amplification of interests," Facebook and Instagram users are "pushed towards extreme dieting and pro-anorexia content very rapidly" -- but that the algorithm perpetuating that could be changed.

After raising new allegations concerning Zuckerberg’s actions, national security concerns, and employee bonuses tied to a system shown to fuel misinformation, Haugen closed with a call to Congress to address Facebook’s growth and provide oversight as it’s historically done for other industries, like tobacco, in the past.

Saying that modern technological systems "walled off," Haugen also called on more whistleblowers with direct knowledge of wrongdoings in big tech to step forward.

"The fact we're being asked these false choices -- it's just an illustration of what happens when the real solutions are hidden inside of companies," she said. "We need more tech employees to come forward through legitimate channels, like the SEC (Securities and Exchange Commission) or Congress, to make sure that the public has the information they need in order to have technologies be human-centric, not computer central."