Under one week: Eyes shut, ears flat to head, skin looks pinkish. Part of umbilical cord may still be attached.
1 week-10 days: Eyes beginning to open, ears still flat. A kitten this age is smaller than your hand.
3 weeks: Eyes are fully open, ears are erect, teeth are visible. Kittens this age are just starting to walk and will be very wobbly.
4-5 weeks: Eyes have changed from blue to another color and/or kittens have begun to pounce and leap. Kittens this age will begin to eat regular cat food.