The egg was a symbol of the rebirth of the earth in Pagan celebrations of spring and was adopted by early Christians as a symbol of the rebirth. The egg is seen as symbolic of the grave and life renewed or resurrected by breaking out of it. The red supposedly symbolizes the blood of Christ redeeming the world and human redemption through the blood shed in the sacrifice of the crucifixion. The egg itself is a symbol of resurrection: while being dormant it contains a new life sealed within it. As easter is during spring-time, and during the time which rabbits and chickens lay eggs/give birth, so it is then associated with new life, etc.