research De Novo Production of Dermal Papilla Cells During the Anagen Phase of the Hair Cycle 41 citations, June 2010 in “Journal of Investigative Dermatology” New cells are added to the hair's dermal papilla during the active growth phase.
research Dedifferentiation of Committed Epithelial Cells Into Stem Cells In Vivo 551 citations, November 2013 in “Nature” Certain mature cells in mouse lungs can turn back into stem cells to aid in tissue repair.