Day 1: Fertilization occurs.
Day 6: Embryo implants in the uterus.
Day 18: Human heartbeat can be detected.
Day 21: Foundations for many organs are apparent.
Day 31: Human anatomy (arms, legs, etc.) develops.
Day 38: Every muscle block is present; baby begins moving independently.
Day 40: Brain waves can be detected.
6 Weeks: EKG and EEG can be done; fingers and toes are forming.
8 Weeks: Every organ system is present, baby is swimming in amniotic fluid.
12 Weeks: Baby has sleep/wake cycle, digests food, swallows, excretes, breathes amniotic fluid, has vocal cords, and cries.