Iwan Bloch (1872-1922), the “father of sexology”, was a Berlin dermatologist. His many socio-cultural studies in sexology earned him an international reputation as a medical historian. He also discovered the Marquis de Sade‘s manuscript of the “120 days of Sodom” in 1904, which had been believed to be lost. He often published his more controversial works under the pseudonym of Eugène Dühren.