There appears to be no biological explanation for this phenomenon, it seems to be merely an inherent talent. Estreens are predominantly females, although male Estreens are not unheard of. Some evidence suggests the psychological makeup of an individual also plays a role. It is theorized, however, that under extreme stress and with great motivation, that one who is not an Estreen may be able to control the morphing process in some way.
Andalite Estreens can make a living based on their talent. For example, Estrid's mother is a morph dancer and Ax has mentioned morph artists. While the talent is considered mostly aesthetic, it can be useful in rapid morphing or in morphing clothes.
- Estreens are predominantly females although male Estreens are not unheard of.