Vatican City is home to some of the most famous art in the world. St. Peter's Basilica, whose successive architects include Bramante, Michelangelo, Giacomo della Porta, Maderno and Bernini, is a renowned work of Renaissance architecture.
This is when the baby's brain, spinal cord, heart and other organs begin to form. The embryo is now made of three layers. The top layer â the ectoderm â will give rise to your baby's outermost layer of skin, central and peripheral nervous systems, eyes, inner ears, and many connective tissues. Your baby's heart and a primitive circulatory system will form in the middle layer of cells â the mesoderm.
The origin of embryonic stem cells. Embryonic stem cells are grown from cells found in the embryo when it is just a few days old. In humans, mice and other mammals, the embryo is a ball of approximately 100 cells at this stage.It is known as a blastocyst and has two parts:1  An outer layer of cells, or trophectoderm, will form the placenta that supports the embryo as it grows inside the uterus. 2  An inner clump of cells, called the inner cell mass, is a ball of 10â20 cells. 3  These cells are undifferentiated, or unspecialized.t is known as a blastocyst and has two parts: 1  An outer layer of cells, or trophectoderm, will form the placenta that supports the embryo as it grows inside the uterus. 2  An inner clump of cells, called the inner cell mass, is a ball of 10â20 cells. 3  These cells are undifferentiated, or unspecialized.