Meta, the technology giant behind Facebook, Instagram and WhatsApp, is facing a landmark trial in the United States over allegations that it deliberately designed its social media platforms to keep children hooked while failing to adequately protect their safety and privacy.

The trial got underway in federal court in Oakland, California, on Tuesday, with 29 U.S. states involved in the wider legal action against the company.

California, Colorado, Kentucky and New Jersey are leading the state consumer-protection claims being heard during this stage of the proceedings, while claims involving all 29 states under federal children’s privacy law are also part of the case.

The states accuse Meta of designing Facebook and Instagram with features that encourage young people to remain on the platforms for extended periods, despite allegedly knowing about potential risks to their mental health and well-being.

Features including infinite scrolling, notifications and recommendation systems are among those under scrutiny.

The lawsuit also alleges that Meta violated the Children’s Online Privacy Protection Act by collecting personal information from children under 13 without obtaining the required parental consent.

Meta denies the allegations and maintains that it has invested heavily in protecting teenagers online. The company is expected to argue that the states have failed to establish that its platforms directly caused the harms alleged and will highlight safety measures introduced over the years.

The case could carry enormous financial and operational consequences for the social media company.

Potential penalties could run into the hundreds of billions of dollars if Meta is found liable, while the states are also seeking changes to the way Facebook and Instagram operate. Meta has previously said calculations under the states’ legal theories could result in penalties as high as $1.4 trillion.

The trial is being overseen by U.S. District Judge Yvonne Gonzalez Rogers and is expected to last several weeks.

An eight-member advisory jury will hear the evidence, although its eventual verdict will not be binding. The final decision on Meta’s liability will rest with the judge.

Some of Meta’s most senior executives are expected to take the witness stand, including Chief Executive Officer Mark Zuckerberg and Instagram head Adam Mosseri.

The trial comes amid growing legal pressure on social media companies over their treatment of children and teenagers.

Earlier this month, a New Mexico court ordered Meta to pay $567 million and imposed measures aimed at protecting younger users. Meta has disputed that ruling and plans to challenge it.

The Oakland proceedings are being closely watched because their outcome could extend well beyond Meta.

A ruling against the company could influence future cases involving social media platforms and help determine how far technology companies can be held legally responsible for features designed to keep young people engaged online.