At approximately day 1

Paramesonephric (Mullerian) ducts form.

Reference

Larsen WJ. 1997. Human Embryology. New York: Churchill Livingstone Inc.

At approximately day 1

Thickening of the thoracic region (mammary crest), forms a 4-6 cell wide ridge. The rest of the milk streak begins to involute.

Duration: 1 week

Reference [PubMed Link]

Gusterson BA, Stein T. 2012. Human breast development. Seminars in Cell and Developmental Biology 23(5):567-573.

At approximately day 1

Oocytes have the capacity to undergo meiosis, but meiosis is not yet initiated.

Reference [PubMed Link]

Rabinovici J, Jaffe RB. 1990. Development and regulation of growth and differentiated function in human and subhumand primate fetal gonads. Endocrine Reviews 11(4):532-557.