Digitama

Digitama (デジタマ)
The eggs from which Digimon are born; they are the beginning and the end of all Digimon. They come in a variety of colors, shapes, and sizes and typically hatch into Baby I Digimon, but will sometimes hatch directly into a higher form, even an Adult Digimon. In rare instances, it is possible for a single Digitama to produce twins.

Etymology
It is a portmanteau of the words "Digital" and "Tamago" (卵), egg in Japanese.