Here's a breakdown:
* Embryo: This term is used to describe an organism in the earliest stages of development, starting from fertilization until the major organ systems are formed.
* Fetus: This term is used after the embryonic stage, when the organism has recognizable human features.
* Zygote: This is the single-celled organism that forms from the fusion of a sperm and an egg.
The specific stages of embryonic development vary depending on the species, but generally involve cell division, differentiation, and the formation of tissues and organs.
