A former professor at the University of California, Los Angeles, Horvath is now principal investigator of the U.K. research arm of Altos Labs, a longevity biotech company that says it is developing therapies that could reverse age-related diseases and disabilities.

Having precise and meaningful ways to measure aging could make it possible for drug developers like Altos Labs to test longevity treatments in people, Horvath says: “It’s a quintessential tool to find interventions for rejuvenation.”

As part of TIME’s series interviewing longevity leaders and influencers, we spoke to Horvath about his pioneering invention and what he thinks might be possible for human life extension.