Transcription: Inside this egg a chick is developing. One of the first organs to form is the heart, which develops after two days of incubation. It pumps blood through a network of vessels that fan out over the yolk. The yolk provides the materials that are used to build structures such as the chick's eyes, which have yet to open after 12 days, and its beak. By 15 days tiny feathers have formed. After 21 days the young bird pecks through the eggs membranes on its way out of the shell. you
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