Zygote: A single-celled human being from fertilization until the first cell division.
Embryo: A human being from the time of the first cell division until approxiamately the eighth week of life.
Fetus: A human being from approximately the eighth week of life up until birth.
Note: To the list above of stages of human development, you should also add newborn, infant, toddler, child, adolescent, adult and senior. Every stage is called something different, but is still human from the moment of conception.
Three Trimesters of Pregnancy
First Trimester: From the moment of conception, until the unborn reaches 12 weeks gestation.
Second Trimester: From 13 weeks until 26 weeks gestation.
Third Trimester: From 27 weeks gestation until the day of birth.
Fertilization: At the very moment of fertilization, you are a human. Each parent contributed 50,000 genes that make up who you are!
3 Weeks:
At three weeks gestation, your parents probably don't know you are there yet, but you are and your little heart is already beating!
6 weeks:
At six weeks gestation, you have a developed brain and nervous system. Your brain waves can actually be recorded! You can respond to touch and your very sensitive.
8 weeks:
At eight weeks gestation, all your major organs are there! You are moving quite a bit, but mom can't feel you yet!
10 weeks:
At ten weeks gestation, your little feet and hands are perfectly formed. Your Skeleton, ears, and eyelids are also formed. By the end of eleven weeks, your sex has been determined!
16 weeks: At 16 weeks gestation, you are 6 inches long. Your little heart pumps 6 gallons of blood a day. Mom can finally start to feel you move. You can feel pain!
20 weeks:
At 20 weeks you can hear the outside world well. You can get startled by loud noises. Your vocal cords are developed and you use them to cry! Don't believe, watch this! dsc.discovery.com/news/media/fetalcryingvideo.html
At three weeks gestation, your parents probably don't know you are there yet, but you are and your little heart is already beating!
At six weeks gestation, you have a developed brain and nervous system. Your brain waves can actually be recorded! You can respond to touch and your very sensitive.
At eight weeks gestation, all your major organs are there! You are moving quite a bit, but mom can't feel you yet!
At ten weeks gestation, your little feet and hands are perfectly formed. Your Skeleton, ears, and eyelids are also formed. By the end of eleven weeks, your sex has been determined!
At 20 weeks you can hear the outside world well. You can get startled by loud noises. Your vocal cords are developed and you use them to cry! Don't believe, watch this!