Hair follicle cells. Fluorescence light micrograph of dermal papilla cells from a human hair follicle. A hair follicle is the structure from which hair grows. Dermal papilla (DP) cells regulate hair follicle development and growth, and are a reservoir of multi-potent stem cells. Fluorescent markers have been used to highlight proteins in the cell nuclei (blue, DAPI stain) and the cytoskeleton (green, vimentin intermediate filament protein).