invagination

/IH0 N V AE0 JH AH0 N EY1 SH AH0 N/
noun
  1. 1

    The process where an anatomical part invaginates upon itself or into another structure.

  2. 2

    One of the methods by which the various germinal layers of the ovum are differentiated.

Source: https://en.wiktionary.org/wiki/invagination