Mark Zuckerberg took the stand Monday to defend Meta’s dominance in the social media landscape as a highly anticipated antitrust trial kicked off in Washington, D.C. The case was brought by the Federal Trade Commission, which alleges Meta, the parent company of Facebook, created a social media monopoly when it acquired Instagram and WhatsApp. If Meta loses the trial, it could be forced to sell off those platforms.

Meta has been under renewed scrutiny in recent weeks as a whistleblower book from a former Facebook public policy director has made international headlines. Meta moved to block the author of “Careless People,” Sarah Wynn-Williams, from promoting her book in the U.S. But Meta’s efforts to silence Wynn-Williams did not prevent her from testifying to a Senate panel last week. Among other things, she revealed how Meta worked with advertisers to target teenage users, including with weight loss and other such products if users displayed signs of body insecurities. She also detailed Meta’s use of censorship.

Sarah Wynn-Williams: “I witnessed Meta work hand in glove with the Chinese Communist Party to construct and test custom-built censorship tools that silenced and censored their critics. When Beijing demanded that Facebook delete the account of a prominent Chinese dissident living on American soil, they did it, and then lied to Congress when asked about the incident in a Senate hearing.”