Figure 1: Qualitative overview of relative levels for individual NR in keratinocyte differentiation by epidermal layer. SB, stratum basale; SS, stratum spinosum; and SG, stratum granulosum are the living layers of the epidermis. Nuclei are degraded by the time cells mature to the upper-most layer, the stratum corneum, and so it is not included. MIN, minimum; MED, medium; and MAX, maximum, reflect levels of staining within levels detected for that NR. Relative comparisons of levels should be made within columns only, not NR to NR across columns especially considering that different representative references [17,18,19,20,21,22,23,24,25,26,27] were consulted for individual NRs, utilizing epidermal tissues derived from different body sites, sun-exposed versus sun-protected regions, unfixed and differently fixed samples, and/or native or antigenretrieved sections.