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.
1.2 Biology (Of a cell, part, or tissue) in the earliest stage of development: primordial germ cells. More example sentences. 1  Embryonic stem cells are primordial cells with the ability to morph into any type of cell in the body.2  During human fetal development, the primordial germ cells migrate to and are incorporated within the developing ovary and are termed oogonia. Embryonic stem cells are primordial cells with the ability to morph into any type of cell in the body. 2  During human fetal development, the primordial germ cells migrate to and are incorporated within the developing ovary and are termed oogonia.