Our most popular series includes these nine models to show the complete stages of development: 4 week-old embryo (25 times life-size), 1st month embryo, 2nd month embryo, 3rd month embryo, 5th month fetus (breech), 4th month fetus, 5th month fetus, 5th month twin fetus, and 7th month fetus (normal). All models are mounted separately on a stand.