invagination
1. [ noun ] the condition of being folded inward or sheathed
Synonyms: introversion
Related terms: condition invaginate
2. [ noun ] (biology) the folding in of an outer layer so as to form a pocket in the surface
Synonyms: infolding introversion intussusception
Examples:

"the invagination of the blastula"

Related terms: organic_process change_of_shape intussuscept
Similar spelling:   invigilation
  invaginate
  invocation