Embryo

An embryo (irregularly from Greek: ἔμβρυον, plural ἔμβρυα, lit. "that which grows," from en- "in" + bryein, "to swell, be full"; the proper Latinate form would be embryum) is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo until about eight weeks after fertilization (i.e. ten weeks after the last menstrual period or LMP), and from then it is instead called a fetus.

The development of the embryo is called embryogenesis. In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote, which possesses half the DNA of each of its two parents. In plants, animals, and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism. The result of this process is an embryo.