In humans as well as many animals, reproduction is sexual^* rather than asexual^*.

Males and females both have organs in their bodies that make sex cells. In males they are called sperm cells and in females they are called egg cells.

When the two types of sex cells meet under certain conditions, they produce a zygote. This process is called fertilization.

After the second week the zygote becomes an embryo until the eighth week of pregnancy. Then the offspring is called a fetus.

A human baby is usually born after about forty weeks of development.