Like homosexuality and other “perversions,” the notion of heterosexuality is a modern invention, in which medical sexology and psychoanalysis played a major role. When psychiatrists in the final decade of the nineteenth century described homosexuals and explained their makeup, some of them also referred to heterosexuals, initially as another group of “perverts,” but soon in terms of normalcy. The highlighting of hetero and homosexuality in the work of Krafft-Ebing, Moll, and Freud underlined the shift from a conception of the sexual impulse as a reproductive instinct toward a view of sexuality that emphasized erotic desire and pleasure in the context of affection and personal fulfilment, irrespective of the reproductive potential.