NCIt definition : An organism in its initial stage of development following fertilization. The human
embryonic period lasts approximately eight weeks, during which time organogenesis
takes place.;
Alternative definition : NCI-GLOSS: Early stage in the development of a plant or an animal. In vertebrate animals
(have a backbone or spinal column), this stage lasts from shortly after fertilization
until all major body parts appear. In particular, in humans, this stage lasts from
about 2 weeks after fertilization until the end of the seventh or eighth week of pregnancy.; CDISC: Early stage in the prenatal development of an animal. This stage occurs from
implantation until closure of the hard palate.;