The scene depicted is set within the house at Mortlake of Dr John Dee (1527–1608). At the court of Queen Elizabeth I, Dee was revered for the range of his knowledge, which embraced the fields of mathematics, navigation, geography, alchemy and chemistry, medicine and optics. He was a Fellow of St John's College, Cambridge, and later one of the original Fellows of Trinity College (he declined a lecturing post at Oxford), and he had an international reputation. In the painting he is showing the effect of combining two elements, either to cause combustion or to extinguish it. Behind him is his assistant Edward Kelly, wearing a long skullcap to conceal the fact that his ears had been cropped as a punishment for forgery. Queen Elizabeth I paid several visits to Dee's house in Mortlake and gave all her support to his research.