what is the meaning of embryonic development?

Hi,

Prenatal development(growth inside uterus) takes place in two stages, namely embryonic development during the first 10 weeks of gestation and then fetal development from the end of tenth week to delivery (usually 36 - 42 weeks, 40 weeks averagely).

During embryonic development the processes of blastulation and gastrulation take place, which are present in all mammals. During blastulation the embryo develops from a single cell to a ball of cells (there is no growth in the size, they just keep dividing so that the size of the ball is roughly equal to the size of the initial embryo) and during gastrulation the embryo which is called blastula at this stage divides to form a three layers the ectoderm, mesoderm and the endoderm from which various body organs develop.

Later during fetal development, organogenesis and maturation occurs in which various organs take their proper structure and position in the body and mature.
During organogenesis the three layers of the gastrula gives rise to various body organs. The brain and skin arises from the ectoderm while the heart, kidneys, blood cells arise from the mesoderm and endoderm gives rise to the inner lining of intestines, lungs, liver etc...

Hope this helps.