During the period of the embryo, the four key changes that take place include: differentiation of cells into specialized tissues and organs, establishment of the basic body plan, development of major organ systems, and initiation of rudimentary limb and facial features.
What career changes for dental assistants took place over four generations? 
Follow this link to see a 30-day embryo (four weeks) http://abluteau.files.wordpress.com/2009/04/limb.jpg
it takes four weeks for the organs of an embryo to form..
Week four
Not exactly. At four weeks, you are just able to detect pregnancy though your pregnancy hormone levels. Your embryo is about the size of a period at the end of a sentence (" . ").
He changes place depending on the time. He could be in route 101, 102 or in his lab
If you were pregnant the developing embryo would be about the size of the head of a pin. The embryo is not the first sign of pregnancy found on ultrasound; the yolk sac shows up long before the embryo is visible. The yolk sac can't be seen uon ultrasound until at least four weeks after the last period.
The four is in the hundredths place.
the answer is iron
Time is the sequence from past to present to future, by which the universe changes. Place is a location in space. Time and place together constitute the four dimensional space-time continuum in which all things are located.
Cell differentiation in a human typically begins around day 4 after fertilization, when the embryo consists of about 100 cells. This process continues as the embryo develops, leading to the formation of different cell types and tissues in the body.
The type of cell division that occurs in the early embryo is called mitosis. Mitosis is a process where a single cell divides into two identical daughter cells, allowing for growth and development of the embryo.