After being a zygote, it becomes a morula. After this, the morula becomes a blastocyst, which is basically cells forming a hollow ball. After these cells divide some more, the blastocyst fills up and becomes an organism with 3 basic parts: the ectoderm, the mesoderm, and the endoderm. This ends up creating a tube through the embryo (the digestive tract) and goes on to form a fetus and eventually a baby.
