You searched for: “differentiation
differentiation (s) (noun), differentiations (pl)
Becoming transformed in the course of development which is not the same as others: There are differentiations in the complexities and organizations of cells, tissues, and body organs as they become progressively more specialized in their formations and functions; especially during the embryonic or pre-birth growth.

The differentiation between the pupae and the larva of a butterfly is easy to determine.

By studying his twin sons carefully, Sandy, their father, noticed some differentiations that helped him to distinguish one boy from the other one.