The modern notion of sexuality took shape at the end of the nineteenth century, especially in the works of Richard von Krafft-Ebing and Albert Moll. This modernisation of sexuality was closely linked to the recognition of sexual diversity, as it was articulated in the medical–psychiatric understanding of what, at that time, was labelled as perversion. From around 1870, psychiatrists shifted the focus from immoral acts, a temporary deviation of the norm, to an innate morbid condition. In the late nineteenth century, several psychiatrists, collecting and publishing more and more case histories, classified and explained the wide range of deviant sexual behaviours they traced. The emergence of medical sexology meant that perversions could be diagnosed and discussed. Against this background both Krafft-Ebing and Moll articulated a new perspective, not only on perversion, but also on sexuality in general. Krafft-Ebing initiated and Moll elaborated a shift from a psychiatric perspective in which deviant sexuality was explained as a derived, episodic and more or less singular symptom of a more fundamental mental disorder, to a consideration of perversion as an integral part of a more general, autonomous and continuous sexual instinct. Before Sigmund Freud and others had expressed similar views, it was primarily through the writings of Krafft-Ebing and Moll that a new understanding of human sexuality emerged.