Lucy Guo, the 30-year-old cofounder of Scale AI, has become the world’s youngest self-made woman billionaire by retaining her stake in the company. Scale AI recently completed a tender offer valuing the firm at $25 billion, an 80% increase since last May. Guo, who left the company years ago, still owns nearly 5% of Scale AI, worth approximately $1.2 billion. Including her stake in her second startup, Passes, her total net worth is estimated at $1.25 billion. Guo cofounded Scale AI in 2016 with Alexandr Wang, who is now the world’s youngest self-made billionaire with a net worth of $3.6 billion. — new from Forbes