In contemporary literary studies, the term ekphrasis refers almost exclusively to a poem created by a poet looking at a painting. In the visual arts and music it is used more broadly to describe intermedial creative processes where, for example, a painting is inspired by a piece of music, or the composition of a piece of music is inspired by a poem. The ekphrasis concept is based on the ancient Greek ἔκϕρασις, which were rhetorical ‘description’ exercises considered important for developing written and perceptual skills. This article considers the gradual recognition by creative writers, and especially novelists, that ekphrasis is a key aspect of their practice. It examines the original purpose of ekphrasis as a rhetorical exercise, then considers how this was interpreted in the time of the first novel writers. It assesses how a technology that changed the way we see – photography – influenced prose writing in the modern era. It looks at how neuroscience and cognitive psychology have attempted to explain what goes on in our minds when we do ekphrasis. And it reports on what writers themselves have said about their visualising techniques. Overall, this article analyses ekphrasis as a key element in the creative writing process.