Science Buddies: "Ask an Expert"

Hello, I'm doing research on stem cells for a project at school, and I'm a bit curious on the question above: What triggers the first differentiation of embryonic stem cells in the early stages of the zygote? Also, how do these early cells regulate differentiation, that is, what is the starting process causes the gene switch to turn on or off for specialization?

Hello,
If you are doing a hands-on science project and you are in grades K-12, please tell us more information about your science project including your hypothesis and your plans for conducting experiments to test that hypothesis. Thank you.