Meta Platforms is facing its most significant trial yet over the harm its social media platforms cause to children, as a case begins this week in California. States are seeking up to $1.4 trillion in damages, which could rival Meta's entire market value, and are demanding changes to how Facebook and Instagram operate. The lawsuit alleges that Meta knowingly designed addictive features that harm youth mental health and collects data on children under 13 without parental consent, violating federal law. The trial in Oakland features four states—California, Colorado, Kentucky, and New Jersey—as plaintiffs, with 25 other states expected to have their cases heard later. Meta denies the allegations, stating its commitment to supporting young people. The stakes are high for Meta, which has already lost two pivotal cases this year and reported a rare profit decline due to $2.4 billion in legal expenses. The $1.4 trillion figure, disclosed by Meta, is nearly as high as its market capitalization, and paying it could lead to bankruptcy and state ownership. Legal experts doubt such a penalty would be imposed, citing precedent. The trial also seeks to hold Meta accountable under state and federal statutes, with potential penalties for each violation. An outcome leading to operational changes could be as consequential as financial penalties. Meta has introduced safety features, but advocates demand more. A New Mexico judge recently ordered additional measures, but only for that state's users. The case is seen as a potential turning point in holding social media companies accountable for youth mental health.