Easter eggs, also called Paschal eggs, are eggs that are sometimes decorated. They are usually used as gifts on the occasion of Easter. As such, Easter eggs are common during the season of Eastertide (Easter season). The oldest tradition is to use dyed and painted chicken eggs, but a modern custom is to substitute chocolate eggs wrapped in colored foil, hand-carved wooden eggs, or plastic eggs filled with confectionery such as chocolate. However, real eggs continue to be used in Central and Eastern European tradition. Although eggs, in general, were a traditional symbol of fertility and rebirth, in Christianity, for the celebration of Eastertide, Easter eggs symbolize the empty tomb of Jesus, from which Jesus resurrected. In addition, one ancient tradition was the staining of Easter eggs with the colour red "in memory of the blood of Christ, shed as at that time of his crucifixion. " This custom of the Easter egg can be traced to early Christians of Mesopotamia, and from there it spread into Russia and Siberia through the Orthodox Churches, and later into Europe through the Catholic and Protestant Churches. The use of eggs in Christianity originates from the ancient pagan customs of worship, which with the advent of Christianity were adapted for it. This process is called religious syncretism.