Embryo

In human development, we call an organism in the early, prenatal stage from about 2 weeks to 2 months after fertilization an embryo. The embryonic stage makes up the majority of the first trimester and is a critical stage for "normal" cognitive and physical development. In addition, the unborn baby is particularly susceptible to health problems (less able to protect itself from illness and every little thing can have sever consequences down the line - much more so than in other stages).