When a fertilized egg begins to divide, the first totipotent stem cells are formed, that is, capable of forming cells of any type. After about four days, they begin to differentiate. The placenta, extraembryonic organs and the embryo itself are formed. At this stage – it is called a blastocyst and has about a hundred cells. There are no longer any typeotent cells; they become pluripotent. Pluripotent stem cells form two populations. The first is a mass of cells located inside the embryo, and subsequently forming various organs of the future organism; the second – future reproductive cells – is first located inside the yolk sac, and later migrates into the formed genital organs.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.