In Buddhism there are several heavens, all of which are still part of "samsara" (illusionary reality). Those who accumulate good karma may be reborn in one of them. However, their stay in heaven is not eternal—eventually they will use up their good karma and will undergo rebirth into another realm, as a human, animal or other beings. Because heaven is temporary and part of "samsara", Buddhists focus more on escaping the cycle of rebirth and reaching enlightenment ("nirvana"). Nirvana is not a heaven but a mental state.