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OpenAI’s Sam Altman rocketed to fame after he released ChatGPT late last year, but a different area of technology has also captured his interest. The tech entrepreneur has invested $180 million in a company that is aiming to defy age and increase the lifespan of humans, MIT Technology Review reported Wednesday.

Retro Biosciences, a San Francisco-based biotech company, announced in April 2022 that it had secured funding for an ambitious mission: to add 10 years to the “healthy human lifespan.” Despite revealing their multi-million dollar funding boost, the source of that funding remained anonymous until now—all of it came from Altman. Retro’s website simply reads: “We are fortunate to have initial funding in the amount of $180 million, which will take us to our first proofs of concept, and secure operation of the company through the decade.”

Altman’s investment in Retro in 2021 is one of the largest investments by an individual in an anti-aging startup, MIT Technology Review reported. The company’s founders are biotech veterans. Joe Betts-LaCroix has advised multiple startups and founded two research-based startups. Sheng Ding is a senior investigator at Gladstone Institute, known for biomedical research, and has launched four other companies. And Matthew Buckley has a background in biotech and healthcare companies, Illumina and Bayer Healthcare.

Betts-LaCroix was also a part-time partner at Y Combinator, a startup incubator that Altman ran from 2014 to 2019. Altman first got interested in health research after reading about studies in which old mice were reinvigorated with the blood of young mice. He later connected with Betts-LaCroix to fund a company that would look into different aspects of aging and biology.

Retro is Altman’s first major investment into biotech, but not his first major tech investment. In 2021, he put $375 million into a fusion energy startup called Helion Energy, which aims to produce limitless clean energy.

“It’s a lot. I basically just took all my liquid net worth and put it into these two companies,” Altman told the MIT Tech Review.

Retro declined Fortune’s request for comment. OpenAI did not immediately return Fortune’s request for comment.

In 2019, Altman became CEO of OpenAI, an artificial intelligence research company. First, the company created an A.I. art tool called DALL-E (unveiled in 2021) that could create a whole host of images from text prompts. And then, last November, OpenAI launched ChatGPT, an internet-famous chatbot that can sustain human-like conversations with its users, answer questions in a matter of seconds and churn out stunningly detailed content from seemingly easy instructions.

Altman isn’t the only Silicon Valley entrepreneur interested in health and longevity. Peter Theil donated millions to nonprofit longevity foundation in 2006, and has predicted “dramatically improved health and longevity for all.” Calico Life Sciences, a company focused on aging research, has been backed by high-profile investors including Google’s parent company, Alphabet. And Altos Labs, a company reportedly backed by tech moguls including Jeff Bezos, announced it had received a $3 billion investment in early 2022. Their stated mission is to reverse diseases, injuries and disabilities through the course of human life. Even the Saudi government said it would invest $1 billion a year to find ways to slow the aging process.

Silicon Valley entrepreneurs have also personally been high-profile dabblers in health and longevity. Bryan Johnson, 45-year-old tech CEO, has spent over $2 million since the start of 2023 on medications and treatments to try and keep himself looking like an 18-year-old. He has dedicated physicians monitoring the aging process in his organs and tracking metrics like his body fat and heart rat.

“The whole longevity field is transitioning into a much more rigorous, clinical place,” George Church, a geneticist at Harvard University, told Bloomberg.

Besides investing millions into the longevity startup, Altman also takes part in his own age-reversing rituals. He reportedly tries to eat healthy, exercises regularly and takes diabetes drug metformin that is believed to increase longevity.