Recent studies in the Tumbar Laboratory have identified heterogenous domains in the interfollicular epidermis of skin based on gene expression patterns. These heterogenous domains are inhabited by two types of stem cells; slow cycling label retaining cells (LRCs) and fast cycling non-LRCs. My work has focused on identifying genetic markers for the slow cycling LRCs. I critically investigated previous microarray data obtained from LRCs and nonLRC analysis to identify genes that were preferentially expressed in LRC domains. Two new potential markers of epidermal LRCs have been identified, however, based on immunofluorescent studies, these two genes were not found to overlap with the strongest LRCs. Instead they overlapped with LRCs that had partially reduced label. These gene expression domains are also spatiotemporally dynamic. Therefore, these midrange LRCs may indicate a third epidermal stem cell population. This opens the way to further functional studies to elucidate the role of gene expression heterogeneity in the epidermis.