the blood in Naples that goes liquid on schedule. saw it with my own eyes, still can't explain it

Grew up half in Naples, my nonna dragged me to the Duomo for this every September and I used to think it was theater. San Gennaro. Bishop, got his head cut off under Diocletian around 305AD. Story goes a woman named Eusebia scooped up his blood in two little glass ampoules. Those ampoules are still ……