A major trial in Los Angeles could shape the future of social media. In a rare courtroom showdown, the industry's biggest players are defending their business models before a jury.

This case isn't just about whether kids use social media. It tests whether companies like Meta and YouTube deliberately designed features that are addictive and harmful to children's mental health. Meta is the parent company of Facebook and Instagram.

"It is our hope and expectation that the social media platforms of tomorrow will be safer than the ones of today," said Matthew Bergman, the founder of the Social Media Victims Law Center.

At the center of the case is a 20-year-old woman who says she started using social media at the age of 10. Her lawsuit argues that the platforms' design features kept her hooked, contributing to depression, anxiety, and struggles with her body image.  

"Those users who have really high problematic media use would be considered the most profitable users for a company. So, they're designing social media in a way that pushes us to be that less healthy user because that's where they make the most money," said Ohio State University Professor Jane Shawcroft.

Internal Meta documents from 2015 estimated millions of children under the age of 13 were on Instagram, and show that CEO Mark Zuckerberg set goals to increase time spent on the app.

Testifying on Wednesday, Zuckerberg said the company's approach has evolved, pointing to current age restrictions and saying, "I wish we could have gotten there sooner."

In a statement, Meta said, "The evidence will show (the plaintiff) faced many significant, difficult challenges well before she ever used social media."

This case is unique because tech giants have long been shielded by limited liability under federal Section 230 law. 

"It basically said that online platforms, like social media companies, could not be held legally responsible for what third-party users posted," said Shawcroft.

But this lawsuit focuses not on user posts, but on how the products themselves were created. The case will be decided by a jury, in a verdict that could influence thousands of similar cases, and help shape how social media platforms are regulated and designed in the future.