The developmental process pertaining to the initial formation of the nipple sheath from the unspecified epidermis. This process begins with a circular ingrowth of the epidermis around the region of the mammary sprout. It ends before the region begins to elevate. [ http://www.ncbi.nlm.nih.gov/pubmed/12558599 GOC:dph ]
This is just here as a test because I lose it