Most of us are familiar with the word "genesis". It means "the beginning" and the beginning of a new plant begins with embryogenesis. An embryo is a young sporophyte and is formed when two haploid gametes, a sperm and an egg, undergo syngamy or fertilization producing a diploid zygote.

      Where exactly does an embryo begin to grow in a plant? This varies depending on the group of land plants being studied. In the Bryophytes and Pteridophytes embryos are found in archegonia, where they are nourished by substances provided by the gametophyte, the haploid generation of the organism. In the gymnosperms and angiosperms, embryos develop inside an ovule, or future seed. Gymnosperm embryos are nourished by the stored food provided by the mega-gametophyte. Angiosperm embryos are nourished by the endosperm tissue that originates when one of the sperm carried by a pollen tube unites with polar nuclei in the embryo sac of a female gametophyte. Once fertilization has occurred, the newly formed zygote divides into an embryo.

      Some plants such as Capsella bursa-pastoris exhibit polarity following division of the zygote into two cells. The cell in the inferior position becomes the suspensor, which pushes the embryo into the endosperm. By the time the embryo of Capsella bursa-pastoris has reached the globular stage, the three tissue systems: (dermal, ground, and vascular) are already present.