Scientists have de-aged the brains of mice by decades.
Experts at the University of California, San Francisco (UCSF) and the University of Queensland in Australia found that - when given the protein PF4 - older mice recovered the sharpness of their younger days.
The team examined the effects of PF4 on two-year-old mice, equivalent to a 70-year-old human, and said that their cognitive function was restored to that of a 30 or 40-year-old.
PF4, a blood cell by platelets, can help restore brain function by calming the immune system and stopping inflammation - which leads to aging in the brain and body.
The research is still preliminary but scientists are optimistic that their "jaw-dropping" findings could be applied to humans.
Dr. Dena Dubal, a professor of neurology at UCSF, said: "When we realised we had independently and serendipitously found the same thing, our jaws dropped.
"The time has come to pursue platelet factors in brain health and cognitive development."