epigenesis

noun

1. (countable, uncountable)The theory that an organism develops by differentiation from an unstructured egg rather than by simple enlarging of something preformed.

   “Ignored for two millennia, Aristotle, in his book On the Generation of Animals, first proposed the theory of epigenesis in biology, suggesting that development of a plant or animal from an egg or spore follows a sequence of steps in which the organism changes and the various organs form.”

2. (countable, uncountable)Changes in the mineral content of rock after its formation.