The gland is able to reach a mature developmental phase under the influence of hormones at the cellular level during the lactation cycle/pregnancy, which impacts severe variations in the macro and microanatomy of this gland, leading to remodeling of the gland into an organ that secretes milk. The female mammary glands’ life cycle in humans is characterized by dramatic changes in structure, composition, and functioning caused by extraordinary variations in gene expression. This differentiates its physiological phases of development, which are all geared toward allowing it to operate as a milk-producing structure after parturition.