The naked areas an artist represents when painting a human body were traditionally not conceived of in terms of skin but of flesh. This chapter discusses notions of flesh and flesh tones in the European art literature from the Middle Ages (Theophilus Prespyter, Cennino Cennini, Jean Lebèque) to French seventeenth and early eighteenth-century art theory. A focus is on the association of flesh and colour in the writings of Roger de Piles and in the technique of colour printing as theorised in Jacob Le Blon's 1725 treatise Coloritto, or the Harmony of Colouring. The chapter demonstrates how skin slowly made its entry into art theory over the course of the eighteenth century and argues that skin and flesh came to be perceived differently over the course of the early modern period. Especially the microscope changed the ways in which the bodily mater was seen: organic substance was now described with textile metaphors as texture or tissue. In accordance with the new medical understanding of the dermis as a tissue built of interwoven layers, eighteenth-century art practice and discourse turned skin into a complex organ that was supposed to be rendered via an appropriately textured painterly brushwork.