Embryonic

Embryonic is an adjective that refers to an embryo or to embryogenesis, the earliest stages of development in living organisms. It is used across biology to describe processes, structures, and stages occurring before birth in animals and before germination in plants. In both fields, embryology studies how a single cell, the zygote, gives rise to a complex organism through cell division, differentiation, and pattern formation.

In mammals, the embryonic period extends from fertilization through about the eighth week of gestation. Early development includes zygote formation, cleavage to a multicellular morula and blastocyst, implantation into the uterine lining, and later gastrulation and organogenesis, during which major organ systems are formed. After the embryonic stage, development typically enters a fetal period characterized by growth and maturation of tissues.

Embryonic stem cells are derived from the inner cell mass of the blastocyst, an early embryo. These cells are pluripotent, able to give rise to many tissue types, and they serve as important tools in basic research and potential regenerative therapies. Their use raises ethical and regulatory considerations that vary by jurisdiction.

In plants, embryogenesis occurs within the seed. The plant embryo forms from a zygote and develops a root and shoot with cotyledons, while the surrounding seed tissues provide protection and nutrients. Plant embryos can also be produced in vitro for breeding and research.

The term embryonic also appears in phrases such as embryonic lethality, which describes death occurring during embryonic development, and embryogenesis, the process of development from fertilized egg to a mature embryo. Overall, the concept centers on the earliest, formative stages of life across diverse organisms.