This comes a day after Facebook users have started to be notified of whether they were among the 87 million people whose data may have been used inappropriately by Cambridge Analytica.
That information was put at the top of users' news feed.
And today, Zuckerberg had to address Congress regarding this matter.
And while some of the questions from the Senators were head-scratchers and certainly proved that some Senators have never even used the social networking app, traders and the market seemed to think Zuck held his own.
And there were definitely a bunch of defining moments. So for some of the great highlights, watch our video above.