An element is a pure substance that is made from a single type of atom. Elements are the building blocks for all the rest of the matter in the world. Examples of elements include iron, oxygen, hydrogen, gold, and helium.
Since the initial discovery that the adult brain contains stem cells that generate new neurons, an important question in neurobiology has been whether or not this adult neurogenesis is functionally important.
1 Melanocyte stem cells are responsible for regeneration of melanocytes, a type of pigment cell. 2  Melanocytes produce the pigment melanin, and therefore play an important role in skin and hair follicle pigmentation. 3  It is not yet certain where these stem cells are found in humans. These stem cells are found in the basal layer of the epidermis. 2  Hair follicle stem cells ensure constant renewal of the hair follicles. 3  They can also regenerate the epidermis and sebaceous glands if these tissues are damaged. 4  Hair follicle stem cells are found throughout the hair follicles.