Organisms in the early stages of growth and development.
In animals, embryos are characterized by the cleavage of the fertilized
eggs to many cells, the laying down of the three germ layers, and formative
steps in organ development. Although
there is some discussion about the characteristics marking the switch from
embryo to fetus, in human beings, embryo generally refers to the time from
implantation to about eight to twelve weeks after conception.
To return to the previous topic,
click on your browser's 'Back' button.