Facebook founder and CEO Mark Zuckerberg began his apology tour on Capitol Hill today, testifying in front of the Senate Judiciary Committee.

Tomorrow, he will appear in front of the House Committee on Energy and Commerce, which is chaired by U.S. Rep. Greg Walden (R-Ore.).

Zuckerberg will address Russian meddling in U.S. election, the harvesting of data by Cambridge Analytica and other misuses of the popular social media platform.

"It's clear now that we didn't do enough to prevent these tools from being used for harm," Zuckerberg will say. "That goes for fake news, foreign interference in elections, and hate speech, as well as developers and data privacy. We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I'm sorry."

Last week, another Oregonian on Capitol Hill—U.S. Sen. Ron Wyden—promised to sponsor federal legislation requiring Facebook to get user permission before collecting data.

"I'm going to bring the hammer down on companies responsible for data breaches," Wyden said.