Forget love letters. Bryan Johnson is saving something a little more personal from Kate Tolo.

The tech entrepreneur turned biohacker has built a following by turning his quest to cheat death into a social media spectacle, documenting everything from his bodily functions to bedroom habits in pursuit of longevity.

His girlfriend is increasingly becoming part of the show — and the couple’s latest science project is being kept on ice.

“Kate’s period blood is in my -80 °C freezer,” Johnson recently wrote on X. “Around 10 mL.”

The crimson keepsake, according to the Blueprint co-founder, is “valuable and underutilized.”

“It’s a non-invasive look into…

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