Mark Zuckerberg is undergoing a two-day congressional inquisition that will be very public — and possibly pivotal for the massive social networking company he created.

Zuckerberg visited with senators in closed-door meetings Monday, previewing the public apology he plans to give Congress on Tuesday after revelations that Cambridge Analytica, a data-mining firm affiliated with Donald Trump’s presidential campaign, gathered personal information from 87 million users to try to influence elections.

He’s apologized many times already, to users and the public, but it is the first time in his career that he has gone before Congress. Zuckerberg will testify before a joint hearing of the Senate Judiciary and Commerce Committees on Tuesday and before a House panel on Wednesday.

In the hearings, Zuckerberg will not only try to restore public trust in his company but also stave off federal regulation that some lawmakers have floated. In prepared testimony released Monday by the House Energy and Commerce Committee, which he is expected to deliver Wednesday, Zuckerberg apologizes for fake news, hate speech, a lack of data privacy and Russian social media interference in the 2016 elections.

“We didn’t take a broad enough view of our responsibility, and that was a big mistake,” he says in the remarks. “It was my mistake, and I’m sorry. I started Facebook, I run it, and I’m responsible for what happens here.”

After resisting previous calls to testify, Zuckerberg agreed to come to Capitol Hill this month after reports surfaced — and the company confirmed — that Cambridge Analytica had gathered Facebook users’ data. In the remarks, Zuckerberg said his company has a responsibility to make sure what happened with Cambridge Analytica doesn’t happen again.

Zuckerberg is also expected to be asked about Russia’s use of U.S. social media during the 2016 elections — a subject of several congressional investigations and special counsel Robert Mueller’s probe into Russian interference.

Zuckerberg on Wednesday testified in front of a House committee, where he faced a second day of grilling by lawmakers. Mark Zuckerberg, the billionaire founder and chief executive of Facebook faced a much tougher crowd on the House side of Capitol Hill in his second day of congressional testimony.

"It is my mistake. I am sorry." - Zuckerberg apologised again, facing criticism from Congress on the second day.