“…During the proliferative phase, under the influence of ovarian-derived estradiol (Ferenczy et al, 1979;Punyadeera et al, 2006), the endometrial glandular epithelium, stroma, and vasculature undergo extensive proliferation. Three dimensional (3D) reconstruction reveals basalis glands form horizontal, branching networks, whereas the functionalis glands grow vertically from these branches (Tempest et al, 2020;Yamaguchi et al, 2020). During the secretory phase, under the influence of ovarian-derived progesterone, the functionalis undergoes changes to prepare for pregnancy; the endometrial epithelial cells differentiate into secretory cells, producing histotroph to nourish an implanting embryo (Burton et al, 2002), regions of stromal cells differentiate into epithelial-like decidual cells, spiral arterioles remodel and uterine natural killer cells become the dominant leukocyte to assist with allorecognition (Gibson et al, 2015).…”