Bryan Johnson, the billionaire tech CEO whose sole goal in life seems to be to live forever, underwent an experimental longevity treatment in the Bahamas last month that involved pumping himself up with 300 million stem cells—and documented it all for his YouTube channel. Johnson, 46, flew out to the Albany, a high-end Bahamas golf resort co-owned by the likes of Tiger Woods and Justin Timberlake, for the procedure. The stem cells, sourced from bone marrow by a company called Cellcolabs, target a patient’s joints in the hopes of “rejuvenating” them, Johnson explained in a June 25 vlog. “Those healthy young Swedish cells should multiply in my body, future-proofing all of my major joints and taking me one step closer to age 18,” he said. The entrepreneur, who all but abandoned Silicon Valley for biohacking and a strict $2-million-a-year regimen he calls “Project Blueprint,” claimed earlier this year to have reversed his epigenetic age by a little over five years.