a science which study the processes and regulations of development of human fetus.(from 1 cell(zygote)to (5-7)X1012 cells total 38 weeks preembryonic period: before 2 weeks---a science which study the processes and regulations of development of human fetus.(from 1 cell(zygote) to (5-7)X1012 cells ) ---total 38 weeks: preembryonic period: before 2 weeks