This week’s highlight is the four-chambered heart, which you can see developing in the tiny bubble on the front of the chest. The blood vessels carry the blood to the newly formed heart, which is beating more than twice as fast as yours.
This week’s highlight is the four-chambered heart, which you can see developing in the tiny bubble on the front of the chest. The blood vessels carry the blood to the newly formed heart, which is beating more than twice as fast as yours.