In the vertebrate nervous system, glial cells include microglia, oligodendrocytes, astrocytes and Schwann cells. In addition, Schwann cells provide insulation for axons and, thus, facilitate axonal transduction of nervous impulses. The crest cells migrate in a ventral direction to give rise to peripheral glia including Schwann cells. Small axons with 0.5–1.5 pm diameters, such as the C fiber nociceptive neurons, the postganglionic sympathetic fibers and some preganglionic sympathetic and parasympathetic fibers, are defined as Remak fibers and are surrounded by nonmyelinating Schwann cells. Schwann cells are recognized as principle glial cells in the peripheral nervous system and play important role in development and maturity. Schwann cells are primarily discussed in the context of their ability in axonal myelination, nerve regeneration and remyelination after injury and various neuropathies. Shortly after birth, Myelinating Schwann Cells and non-myelinating Schwann Cells can be differentiated in peripheral nerves.