Can your taste words, feel flavours as a shape, or hear colours? If so you may well have synaesthesia, a neurological condition that gives rise to a 'merging of the senses.' Julia Simner describes synaesthesia's many forms, and delves into the underlying neuroscience. Explaining the scientific basis for synaesthesia, she considers how we can measure the effects of synaesthesia, childhood development, memory, personality, and artistic creativity, and the potential limitations of synaesthesia might impose.