The is that period of the pregnancy in which there is intense cellular division and specialization.

During the germinal stage, the cells divide intensively. The zygote divide during the process of cleavage, and forms two blastomeres, which then divides into four cells, and so on. 
During the embryonic stage, cells continue to divide rapidly and are also differentiated to perform various functions. Ectoderm, mesoderm, and endoderm are formed, as the three germ layers. 
Till week 8. the process of differentiation continues, and a fetus develops from the embryo, during this time.