In Tibetan Buddhist belief, rebirth is central to the entire structure of existence. Death is the bridge between lives. It's the end of one life, but at the same time it's also the necessary prelude to rebirth in a new life, which will also eventually end in death - and so on, across a vast expanse of time, the cycle ending only when enlightenment is attained. Nor is it inevitable that a person will be reborn in human form: there are six realms of existence, and one's next life may be as a god or titan, an animal, a hungry ghost, or an inhabitant of the terrible hell realms. For a Tibetan Buddhist, death changes - or at least can change - everything, and it is because of this huge potential that death is by far the most significant life-cycle event. The importance of rebirth is a major influence on how Tibetan Buddhists approach dying and death and how they conduct the funerary rituals for a deceased loved one. There are many regional variations in the performance of these rites: this article will focus on certain common themes running through them.