Live Chicken Embryos

Take a look at living chicken embryos in various stages of development.

It takes just 21 days for an egg to go from just laid to newly hatched chick, and a lot goes on in just the first week. Look closely and you’ll find blood vessels, a backbone, wing buds, eyes, a brain, and—throbbing prominently by day 5 or so—a beating heart.

Chick Embryo Development

What’s going on?

The life of a chicken embryo begins inside the hen, before the egg is laid. A rooster deposits sperm into the hen’s reproductive tract. A sperm unites with a yolk cell, forming an embryo. The hard shell then grows around the yolk before it is laid.

After an egg is laid, an incubated egg develops quickly. What starts as a white spot on day one develops visible blood vessels on day two. Four or five days after being laid, the embryo has a visible backbone and a beating heart. After six or seven days, the wing buds, eyes, and brain are visible.

Day 1

(after hen lays egg and starts incubating it)
Look for the white embryo in the center of the nutrient-rich yolk. All the embryos here look similar to developing human embryos.
(click diagram to enlarge)

Day 2

Look for developing blood vessels that will connect the embryo to the yolk, its source of food. This embryo has about four times as many cells as on day 1.
(click diagram to enlarge)

Days 3 to 4

Look for a backbone, blood vessels, and a beating heart. This embryo has four to fifteen times as many cells as a day 2 embryo.
(click diagram to enlarge)

Days 5 to 7

Look for the tiny wing buds, eyes, and brain. At this stage it still looks a lot like a human embryo. By day 21, the chick would be ready to hatch.
(click diagram to enlarge)