To be considered for sainthood, a person must be dead and have performed two miracles while living, according to the Roman Catholic Church.

Leo canonized Carlo Acutis, who died in 2006, during an open-air Mass in St. Peter’s Square that was attended by tens of thousands of people, many of them millennials and couples with young children.

Pope Leo XIV proclaimed the Italians Pier Giorgio Frassati and Carlo Acutis as saints of the Church on Sunday, Sept. 7.