As part of the legacy handed down from its Jewish roots incense is used during all services in the Eastern Orthodox Church. It is burned as an offering of worship to God even as it was done in the Jewish temple. Traditionally, the base of the incense used is the resin of "Boswellia thurifera", also known as frankincense, but the resin of fir trees has been used as well. It is usually mixed with various floral essential oils giving it a sweet smell. Incense represents the sweetness of the prayers of the saints rising up to God (Psalm 141:2, Revelation 5:8, Revelation 8:4). The incense is burned in an ornate golden censer that hangs at the end of Three chains representing the Trinity. In the Greek tradition there are 12 bells hung along these chains representing the 12 apostles; the Slavic churches usually do not have bells. The censer is used (swung back and forth) by the priest/deacon to venerate all four sides of the altar, the holy gifts, the clergy, the icons, the congregation, and the church structure itself.