Formation of myelin sheath.
D000818:Animals; D001369:Axons; D051379:Mice; D008854:Microscopy, Electron; D009186:Myelin Sheath / Q000166:cytology*; D009413:Nerve Fibers, Myelinated / Q000166:cytology; D051381:Rats; D012583:Schwann Cells / Q000166:cytology