Skip Navigation
The Endowment for Human Development
The Endowment for Human Development
Improving lifelong health one pregnancy at a time.
Donate Now Get Free Videos

Slideshow: Early Events

Four-Cell Embryo

#43, Slide 6 of 24

48 hours

Source: Centro Riproduzione Assistita, Catania, Italy.

Label Key:

1. blastomere #1
2. blastomere #2
3. blastomere #3
4. blastomere #4
5. zona pellucida
6. inside border of zona pellucida
7. perivitelline space
All ages referenced to fertilization, not last menstrual period.
Tell your story. Create your own pregnancy calendar.
When does health begin? Find out now.