The hearings were a major test for Zuckerberg.
However Facebook's stock remains 10 percent below where it stood before news of the privacy scandal broke last month, a decline that has wiped out about USD$50 billion in shareholder wealth.
On the question from Jan Schakowsky, a Democrat from IL, about how many companies did Kogan sell the data from Facebook to, Zuckerberg said that there are a handful of companies who got the user data harvested by Cambridge Analytica and he will follow up.
CA has been accused of mining personal information of millions of Facebook users illegitimately to help political campaigns and influence polls in several countries.
The latest estimate of affected users is up to 87 million.
And Lujan had more hard questions for the Facebook founder.
Patience with the social network had already worn thin among users, advertisers and investors after the company said last year that Russian Federation used Facebook for years to try to sway USA politics, an allegation Moscow denies. Zuckerberg told Congress that the firm got some of his information. He did not offer specific details about how Facebook would improve diversity within the company.
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The 33-year-old tech big-wig, poised and stone-faced on Tuesday, also repeatedly apologized for Facebook's role in the data-mining scandal, adding the company is reviewing the improper access third-party apps may have to data on the social network site. It's not clear what that regulation would look like.
Zuckerberg said regulation of social media companies is inevitable, but warned that rules could also hamper the industry's growth. But he warned that lawmakers should be careful in what they propose.
Mr Zuckerberg warned that lawmakers should be careful in what they propose and noted that larger companies like Facebook have more resources to comply with regulations than small startups.
The multibillionaire began the second day of his hearing on Capitol Hill, Washington, at 10am ET (3pm BST) today. That data ended up with Cambridge Analytica, a data analysis firm that did political work during the 2016 election. They posted their biggest daily gain in almost two years on Tuesday as Zuckerberg managed to deter any specific discussion about new regulations that might hamper Facebook's ability to sell ads tailored to users' profiles.
On Tuesday he batted away often-aggressive questioning from members of the Senate Judiciary and Commerce committees who accused him of failing to protect the personal information of millions of Americans from Russians intent on upsetting the USA election.
The 33-year-old tech mogul was on Capitol Hill to face a second day of grilling from United States lawmakers over the data leak scandal which saw 87 million users - including 1 million Brits - have their personal info harvested.
35% said they were using Facebook less than they used to over the privacy issue.