Nevi are the strongest risk markers of melanoma. Common nevi are still regarded clinically as a single entity, despite data suggesting that nevi consist of distinct subsets, and a new classification reflecting the diversity of nevi is needed. However, classifications by clinical examination or even by low-resolution imaging techniques have been limited by difficulty to correlate with histopathology, the gold standard for diagnosis, and by lack of specific pattern in a substantial percentage of nevi.We propose to harness Reflectance Confocal Microscopy (RCM), a cutting-edge, high resolution imaging technology to more precisely classify nevi and follow their evolution over time. In addition, we will correlate RCM pattern of nevus subsets to their respective histopathologic patterns and characterize their genetic profiles. We will image with RCM common nevi from the back and legs of patients and characterize nevus subsets that show distinctive RCM patterns. We will then test the reproducible assignment of RCM images of nevi to these subsets. After one year, we will repeat RCM imaging of the same nevi and examine whether distinct RCM patterns of nevus subsets are retained over time. In addition, we will identify patients with common, banal-appearing nevi that have been scheduled for excision by physicians outside the scope of the study; we will image these nevi prior to excision and then test whether distinct RCM patterns of nevi correlate reproducibly with unique histopathologic patterns. Finally, we will draw a preliminary link between RCM nevus patterns and their genetic profiles by testing excised nevus tissue for BRAF mutation.The resulting state-of-the-art classification of nevi could impact patient care since different nevus subsets may vary in associated melanoma risk. More precise characterization of nevi in patients will identify individuals at high melanoma risk that would be prime target for screening and intervention efforts.