Oligodendrocytes from stem cells, fluorescence light micrograph. Stem cells are able to differentiate into the many cell types in the human body. The type of cell they mature into depends upon the biochemical signals received. In this case, neural stem cells have matured into oligodendrocytes, support cells that form the myelin sheaths around nerve fibres in the central nervous system (brain and spinal cord). These cells have been stained by an oligodendrocyte marker called O4 (green) and DAPI (blue). DAPI is used to stain cell nuclei. This culture is from human tissue.