Digimon hatch from eggs called Digi-Eggs/Digitama. In the English iterations of the franchise there is another type of Digi-Egg that can be used to digivolve, or transform, Digimon. This second type of Digi-Egg is called a "Digimental" in Japanese. They age via a process called "Digivolution" which changes their appearance and increases their powers. The effect of Digivolution, however, is not permanent in the partner Digimon of the main characters in the anime, and Digimon who have digivolved will most of the time revert back to their previous form after a battle or if they are too weak to continue. Some Digimon act feral. Most, however, possess large amounts of intelligence and human speech. They are able to digivolve by the use of Digivices that their human partners have. In some cases, as in the first series, the DigiDestined (known as the 'Chosen Children' in the original Japanese) had to find some special items such as crests and tags so the Digimon could digivolve in another further stages of evolution known as Ultimate and Mega in the dub.

The first Digimon anime introduces the Digimon life cycle: They age in a similar fashion to real organisms, but do not die under normal circumstances because they are made of reconfigurable data. Any Digimon that receives a fatal wound will dissolve into infinitesimal bits of data. The data then recomposes itself as a Digi-Egg, which will hatch when rubbed gently, and the Digimon goes through its life cycle again. Digimon who are reincarnated in this way will sometimes retain some or all their memories of their previous life. However, if a Digimon's data is completely destroyed, they will die.

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