an organism in early stages of development, before hatching
from an egg.
Human: A fertilized egg that has begun cell division,
often called a pre-embryo (for pre-implantation embryo).
An embryo is now defined as a later stage, i.e. at the
completion of" the pre-embryonic stage, which is
considered to end at about day 14. The term, embryo, is
used to describe the early stages of fetal growth, from
conception to the eighth week of pregnancy.