Proembryo

Proembryo, or pro-embryo, is a botanical term that has been used for centuries, to denote the series of cells that are formed after fertilization within the ovule of a flowering plant, before formation of the embryo.

More recently, this same term has been given a more extensive meaning, with reference to human egg cells (ova) that have been fertilized but not yet implanted into a uterus. This more recent meaning is synonymous with "preembryo" or "pre-embryo," and corresponds to stages with more accepted terms zygote and blastocyst.