Instagram head Adam Mosseri testified before Senate lawmakers Wednesday and was pressed on the app's impacts on young children and teens.

Why it matters: Legislation to protect kids online is one area Congress has shown it's willing to regulate, as Axios previously reported. Wednesday's back-and-forth gave momentum to lawmakers eager to make more rules for social media platforms and how children and teens can use them.

Details: Lawmakers questioned Mosseri on internal research from Meta, Instagram's parent company, tried to get him to support bills and brought up ways their staff was able to find harmful content on the app that is supposed to be banned.

Four key moments:

1. Mosseri did not commit to never pursuing an Instagram for Kids app in a back-and-forth with Sen. Richard Blumenthal (D-Conn.): "What I can commit to today, is that no child between the ages of 10 of 12, should we ever manage to build Instagram for 10- to 12-year-olds, will have access to that without their explicit parental consent," said Mosseri.
2. Senators managed to catch Mosseri off-guard a few times about Instagram policies: Sen. Marsha Blackburn (R-Tenn.) pressed Mosseri on an interview he did with popular dancer and influencer JoJo Siwa, who said in a June interview she's been on Instagram since age 8, which is against the platform's rules. "That was a missed opportunity," to address underage kids using Instagram use, Mosseri said.
3. Mosseri also revealed during questioning by Blackburn that Instagram made accounts for those under the age of 16 on iOS and Android private by default, but had not done so on desktop.

3. Mosseri hesitated to say Instagram was addictive or bad for mental health: Lawmakers referenced a recent Surgeon General report that says certain kinds of online activity "likely do harm some young people." Mosseri said he does not believe research shows that social media drives a rise in suicides, and told Sen. Dan Sullivan (R-Alaska) that he was selectively interpreting the Surgeon General report.

4. Instagram will soon let users go back to a chronological feed. Mosseri said Instagram is working on a content feed to let users sort their feeds chronologically, like Instagram used to be prior to 2016, and will roll it out early next year.

Go deeper: Instagram's boss faces Congress' questions on harm to teens

Editor's note: This story has been corrected to reflect that Sen. Dan Sullivan represents Alaska, not Arkansas.