After incubation begins, rapid cell division starts. The embryo exists as a flat disc of cells on the yolk surface. No organs are formed yet.

Key developments:

• Cell division accelerates

• Embryo remains microscopic

• No visible structures

Early structure appears. The embryo begins organizing into layers that will form major systems.

Key developments:

• Primitive heart tube forms and begins beating

• First blood vessels appear

• Neural tube begins forming

This is the first dramatic growth phase.

Key developments:

• Heartbeat is clearly established

• Spine begins forming

• Limb buds appear

• Blood vessel network expands rapidly

The embryo begins to resemble a vertebrate.

Key developments:

• Head enlarges

• Eye pigment begins forming

• Limb buds elongate

• Amniotic sac fully surrounds embryo

Distinct chick traits start appearing.

Key developments:

• Beak formation begins

• Brain regions differentiate

• Legs and wings lengthen

• Embryo begins spontaneous movement

The embryo becomes clearly bird-like.

Key developments:

• Toes start separating

• Eye darkens noticeably

• Major organs continue forming

• Blood vessels thicken and strengthen

Internal systems become more complex.

Key developments:

• Skeleton begins ossifying

• Sex organs begin forming (not externally visible)

• Beak hardens

• Embryo size increases significantly

External development becomes more refined.

Key developments:

• Feather tracts form beneath the skin

• Wing and leg joints develop

• Eyelids begin forming

• Movement becomes stronger

Chick features sharpen.

Key developments:

• Claws begin forming

• Beak shape becomes distinct

• Muscles strengthen

• Blood vessels remain prominent

Growth slows slightly as refinement increases.

Key developments:

• Bones continue hardening

• Muscle coordination improves

• Eyelids cover most of the eye

• Chick responds to movement

Surface structures mature.

Key developments:

• Scales form on legs

• Feather follicles deepen

• Beak continues hardening

• Chick movement becomes smoother

The chick looks complete in form.

Key developments:

• Feather tracts expand

• Egg tooth becomes visible

• Proportions balance out

• Movement remains frequent

External texture begins changing.

Key developments:

• Feathers begin pushing outward

• Skin thickens

• Muscle tone improves

• Chick occupies more space in the egg

Growth becomes more about mass than shape.

Key developments:

• Feather coverage increases

• Movement slows slightly

• Bones and muscles strengthen

• Chick fills much of the egg

Energy storage becomes critical.

Key developments:

• Yolk sac starts pulling inward

• Digestive system prepares for use

• Chick movement becomes deliberate

• Space inside egg tightens

Changes are mostly internal now.

Key developments:

• Muscles strengthen for hatching

• Lungs prepare for breathing air

• Yolk sac remains mostly external

• Chick growth becomes denser

Preparation overtakes growth.

Key developments:

• Feathers nearly complete

• Chick begins conserving energy

• Blood vessels start receding

• Turning still required

Major management shift.

Key developments:

• Yolk sac rapidly absorbs

• Chick positions head toward air cell

• Turning stops

• Humidity is increased

The chick is ready.

Key developments:

• Beak tucks under right wing

• Chick internally pips into air cell

• Lung breathing begins

• Movement is minimal but purposeful

Hatching begins.

Key developments:

• Chick breaks shell membrane

• External pip appears

• Chick rests between efforts

• Blood vessels fully retract

The chick emerges.

Key developments:

• Shell is zipped open

• Chick exits egg

• Down is wet and matted

• Yolk sac fully absorbed

The chick rests before standing and drying.