Final answer:
Early encounters with Christianity took place in the first century CE, with the emergence of Christianity as a distinct religion and its spread in the Roman-controlled Mediterranean world. The conversion of Roman Emperor Constantine in the early 4th century further influenced its growth and eventual establishment as the official state religion.
Step-by-step explanation:
Some of the earliest encounters with Christianity occurred in the first century CE. Christianity emerged as a distinct religion and spread into communities around the Roman-controlled Mediterranean world. One notable early Christian community was founded in the Egyptian city of Alexandria. The Roman Emperor Constantine's conversion in the early 4th century and his subsequent legalization of Christianity played a significant role in the spread and establishment of Christianity as the official state religion in the Roman Empire.