The trial started off on Tuesday with a battle of words and facts.

Paul Schmidt, a lead attorney for Meta in the trial, directly addressed an internal research report that Megan O'Neill, a lead attorney for California, made part of the states' opening arguments.

The Meta document O'Neill showed the jury found that "1 in 5 teens says Instagram makes them feel worse".

Schmidt said: "That sounds pretty bad."

"What else does the document say?" Schmidt went on.