Little is known about the life of Januarius. He is believed to have been martyred in the Emperor Diocletian’s persecution of 305. Legend has it that Januarius and his companions were thrown to the bears in the amphitheater of Pozzuoli, but the animals failed to attack them. They were then beheaded, and Januarius’ blood ultimately brought to Naples.
“A dark mass that half fills a hermetically sealed four-inch glass container, and is preserved in a double reliquary in the Naples cathedral as the blood of St. Januarius, liquefies 18 times during the year…Various experiments have been applied, but the phenomenon eludes natural explanation…
On 19 September 305, Gennaro, bishop of Benevento, was beheaded in Pozzuoli during the persecution of Christians by Diocletion.
The blood gushed due to the decapitation was collected and kept in an ampoule by Eusebia, who had been his wet nurse In 313, the martyr's body was being moved to Naples, and the procession stopped to rest in what would be today's piazza Bernini, in the area known as Vomero. Eusebia put the vials containing the martyr's blood near his head, and the blood started to melt, at the presence of the local bishop.
San Gennaro was named patron and protector of the city, and is invoked by the people of Naples on several occasions, to ask for help, healing and special favors. Meanwhile, with very few exceptions, the blood miracle happens again and again.