Paul Langerhans was one of the most brilliant scientific observers of his time, contributing considerably not only to medicine but also to zoology by describing new species of invertebrates (De Panfilis, 1988). He was a medical student at the Berlin Pathological Institute when he discovered in 1868 the epidermal cells that bear his name. He believed that these gold chloride-positive midepidermís dendritic cells were intra-epidermal receptors for extracutaneous signals to the nervous system (Langerhans, 1868). This neural hypothesis prevailed for almost a century.