When Ötzi the Iceman was alive 5300 years ago, eating ibex and deer and traipsing over the Alps, his veins pulsed with blood. But when Ötzi’s frozen, mummified body was discovered in 1991, his vessels were empty; scientists assumed his blood had degraded over time. Now, a team of researchers has zoomed in on two spots on the Iceman’s body: a shoulder wound found with an embedded arrowhead and a hand lesion resembling a stab wound. The scientists used atomic force microscopy, a visualization method with resolution of less than a nanometer, to scan the wounds for blood residue. They discovered red blood cells (inset)—the oldest in the world to be found intact—as well as fibrin, a protein needed for blood to clot, they report today in Journal of the Royal Society Interface. The presence of fibrin indicates that Ötzi didn’t die immediately after being wounded. Next, the researchers plan to study the blood cells for changes in molecular structure due to dehydration and aging. Such analyses could help forensic experts pick up on more subtle changes that reveal the age of younger blood cells, such as those from crime scenes.