A strategy was developed to fluorescently label slow-cycling cells in skin, enabling the identification of label-retaining cells (LRCs) that mark the skin stem cell (SC) niche. These LRCs rarely divide within their niche but change properties when stimulated to exit. Their transcriptional profile defines the niche, with many mRNAs encoding surface receptors and secreted proteins, enabling LRCs to signal and respond to their environment. The epidermis and its appendages undergo continuous renewal, maintaining reservoirs of multipotent SCs. The epidermal basal layer (BL) contains putative SCs and transiently amplifying (TA) cells, which give rise to terminally differentiating suprabasal layers. The BL and hair follicle outer root sheath (ORS) are contiguous and biochemically similar. The hair bulb contains the dermal papilla (DP), which maintains contact with matrix TA cells until they differentiate into the inner root sheath (IRS) and hair shaft. Multipotent epithelial SCs with high proliferative potential reside in the bulge. The bulge contains the majority of infrequently cycling, label-retaining cells (LRCs), which can respond to anagen DP signals to regenerate the follicle. After wounding or transplantation, bulge cells give rise to epidermis, follicles, and sebaceous glands. Additionally, when dissected from rat whiskers and cultured, bulge cells yield more colonies than other follicle segments. To define the SC niche, researchers used transgenic mice expressing histone H2B–green fluorescent protein (GFP) controlled by a tetracycline-responsive regulatory element. This allowed the identification of slow-cycling cells, including LRCs in the bulge. These cells were found to be enriched in CD34 and expressed keratins K5, K14, and K15, but not differentiation-specific K1. Transcriptional profiling revealed that LRCs express mRNAs encoding surface receptors and secreted proteins, which are important for signaling and responding to their environment. These mRNAs include known SC markers such as stem cell factor (kit ligand), Dab2, ephrin tyrosine kinase receptors (Ephs), tenascin C (Tnc), interleukin-11 receptor, Id binding protein-2 (Idb-2), four-and-a-half lim domains (Fhl1), CD34, S100A6, and growth arrest-specific (Gas) proteins. LRCs were found to be involved in TGFβ signaling and Wnt pathway regulation, which are essential for follicle morphogenesis and hair cycle activation. These findings suggest that the bulge SC niche is a growth and differentiation-restricted environment. The LRC-related changes suggest a broader interaction between environmental stimuli and the SC niche.A strategy was developed to fluorescently label slow-cycling cells in skin, enabling the identification of label-retaining cells (LRCs) that mark the skin stem cell (SC) niche. These LRCs rarely divide within their niche but change properties when stimulated to exit. Their transcriptional profile defines the niche, with many mRNAs encoding surface receptors and secreted proteins, enabling LRCs to signal and respond to their environment. The epidermis and its appendages undergo continuous renewal, maintaining reservoirs of multipotent SCs. The epidermal basal layer (BL) contains putative SCs and transiently amplifying (TA) cells, which give rise to terminally differentiating suprabasal layers. The BL and hair follicle outer root sheath (ORS) are contiguous and biochemically similar. The hair bulb contains the dermal papilla (DP), which maintains contact with matrix TA cells until they differentiate into the inner root sheath (IRS) and hair shaft. Multipotent epithelial SCs with high proliferative potential reside in the bulge. The bulge contains the majority of infrequently cycling, label-retaining cells (LRCs), which can respond to anagen DP signals to regenerate the follicle. After wounding or transplantation, bulge cells give rise to epidermis, follicles, and sebaceous glands. Additionally, when dissected from rat whiskers and cultured, bulge cells yield more colonies than other follicle segments. To define the SC niche, researchers used transgenic mice expressing histone H2B–green fluorescent protein (GFP) controlled by a tetracycline-responsive regulatory element. This allowed the identification of slow-cycling cells, including LRCs in the bulge. These cells were found to be enriched in CD34 and expressed keratins K5, K14, and K15, but not differentiation-specific K1. Transcriptional profiling revealed that LRCs express mRNAs encoding surface receptors and secreted proteins, which are important for signaling and responding to their environment. These mRNAs include known SC markers such as stem cell factor (kit ligand), Dab2, ephrin tyrosine kinase receptors (Ephs), tenascin C (Tnc), interleukin-11 receptor, Id binding protein-2 (Idb-2), four-and-a-half lim domains (Fhl1), CD34, S100A6, and growth arrest-specific (Gas) proteins. LRCs were found to be involved in TGFβ signaling and Wnt pathway regulation, which are essential for follicle morphogenesis and hair cycle activation. These findings suggest that the bulge SC niche is a growth and differentiation-restricted environment. The LRC-related changes suggest a broader interaction between environmental stimuli and the SC niche.