In the 5th week or 3rd month also known as EMBRYONIC stage of development, the developing individual is less than an inch long, and has developed a rudimentary beating heart, a brain, an intestinal tract, and a number of other organs that are at a primitive stage of development.
During this stage, the embryo has three layers that will give way to the development of the baby's skin, bones, muscles, reproductive system, kidneys, lungs, intestines, and bladder.
