It's unclear what body part or body fluid is present. The vial of the relics of Nicholas, Bishop of Myra in Lycia (present-day Turkey), the person known to us as Santa Claus, appears to contain dust.
Some day we'll be able to recreate saints from their relics, sort of like the dinosaurs of Jurassic Park. I'd call it "Apostolic Park." I propose first to reanimate St. Christina the Astonishing, who, at her funeral, flew up out of her coffin and sat in the church's rafters.