Elon Musk and Sam Altman founded OpenAI together, but now trade barbs. Here's the history of their working relationship and feud.

• Elon Musk helped found OpenAI, but he has frequently criticized it in recent years.
• Though he recently sued OpenAI and CEO Sam Altman, he has since dropped the lawsuit.
• Here's a history of Musk and Altman's working relationship.

Elon Musk and Sam Altman lead rival AI firms and now take public jabs at each other — but it wasn't always like this.