Christianity began in the 1st century AD as a Jewish sect but quickly spread throughout the Greco-Roman world.
Although it was originally persecuted under the Roman empire, it would ultimately become the state religion. In the Middle Ages it spread beyond the old borders of the Empire into Northern Europe and Russia. During the Age of Exploration, Christianity expanded throughout the world; it is the world's largest religion.
Throughout its history, the religion weathered schisms and theological disputes that have resulted in the development of three main branches: Catholicism, Eastern Christianity (Eastern Orthodoxy), and Protestantism.