San Francisco, Sep 17 (IANS): Tesla and SpaceX CEO Elon Musk was "lonely and sad" as a child as he struggled to make friends in school, his new biography by American author-journalist Walter Isaacson has claimed.

He also struggled to understand social cues and had to rely on books to learn about them, reports Insider.

In the biography, Isaacson wrote that the billionaire's mother Maye Musk put him in the nursery at three years old because he was "intellectually curious," despite the principal's warnings that he would experience social challenges as he was younger than anyone else in the class.

"It was a mistake. Elon had no friends, and by the time he was in second grade he was tuning out," Isaacson wrote.

Moreover, Musk's mother told Isaacson that he "became so lonely and sad," when he started going to school.

"Kimbal and Tosca would make friends on the first day and bring them home, but Elon never brought friends home. He wanted to have friends, but just didn't know how," Isaacson mentioned in the biography.

Tesla's chief revealed his problems were due to Asperger's, a form of Autism Spectrum Disorder, which made him "bad at picking up social cues", the report stated.

"I took people literally when they said something. And it was only by reading books that I began to learn that people did not always say what they really meant," Musk told Isaacson.

Meanwhile, the biography also revealed that Musk and billionaire philanthropist Bill Gates got into a verbal spat after the Tesla CEO confronted the Microsoft founder over shorting the electric-car company's shares last year.

Isaacson wrote that in early 2022, Gates spoke to Musk and said he wanted to "come see (him) and talk about philanthropy and climate" at a meeting.

The meeting happened at Musk's Texas plant where the SpaceX owner confronted Gates over the decision to short Tesla stock.