Christianity began in the 1st century AD as a Jewish sect that believed Jesus was the Messiah, but it quickly spread throughout the Roman Empire. Jesus taught about loving others and that there is only one God, and he performed miracles that made him popular, though his teachings threatened religious and Roman authorities, who crucified him. After his resurrection, his followers announced he was the Messiah and their religion grew rapidly, spreading beyond Jews through the missionary efforts of Paul of Tarsus. Today Christianity has over 2 billion followers worldwide and maintains core beliefs that Jesus is the son of God and the path to salvation.