Uterus (receptive stage). Coloured scanning electron micrograph (SEM) of the lining or endo- metrium of the human uterus during the receptive stage of the menstrual cycle. The lining builds up (proliferation) in the first 14 days of the cycle to prepare for pregnancy, an egg is released at the receptive stage when fertilisation occurs, and then the lining becomes secretory to nourish the embryo. If no pregnancy occurs, it breaks down at menstruation after 28 days. Here, epithelial cells known as pinopodes (red) occur at the recep- tive stage and last only about 48 hours. Secretory cells (green) and ciliated cells (hair-like) are also seen. Magnification: x1,700 at 5x7cm size. x6,000 at 8x10"~LANDSCAPE"