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.
A thin-walled hollow structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises. The outer layer of cells gives rise to the placenta and other supporting tissues needed for fetal development within the uterus while the inner cell mass cells gives rise to the tissues of the body.