The mammary gland undergoes a series of structural and functional growth and differentiation depending on the reproductive stages of animals. The secretory tissue of the mammary gland is developed from ectoderm but associated connective tissues, adipose tissues, and smooth muscles are derived from mesoderm. Mammary stem cells (MaSCs) are multipotent adult stem cells of epithelial origin that give rise to different cellular components of the mammary gland. The specification of the mammary line is governed by different molecular signaling pathways, which subsequently develop into the formation of placode and mammary bud. Prenatal mammogenesis is characterized by the development of basic mammary structures with partially formed connective tissue, blood vessels, and lymph vessels. A notable development of the mammary gland with lobuloalveolar growth occurs after puberty, with the influence of reproductive hormones. It was estimated that 48–94% of mammary growth occurs during gestation in cows, which mostly constitutes the growth of mammary parenchyma and duct system. Lactational mammogenesis is characterized by an increase in secretory tissues that constitute 10% of mammary growth. The development of the mammary gland is regulated by ovarian hormones (estrogen and progesterone) and hypophyseal hormones (prolactin and growth hormone), along with placental lactogen, glucocorticoids, and oxytocin. There are several growth factors required for mammogenesis like insulin-like growth factor (IGF), epidermal growth factor (EGF) family, platelet-derived growth factor (PDGF), and transforming growth factor-β (TGF-β).