Blue is a favourite colour of people around the world. But the production of intense blue presents challenges to nature. Most vertebrates are unable to produce blue pigment. The orange of kingfisher plumage is the product of tiny pigment granules but its cyan and blue feathers contain no pigments. These colours are ‘structural’. They are created by the intricate structural arrangement of a transparent material which, depending on its precise make-up and thickness compared to the tiny wavelength of light, produces a range of colours by ‘incident light’ – in other words light shining on the sample. Structural colours feature in plants too – particularly in fruit and flowers. In research published in 2012, Vignolini and others revealed how an African plant called the Pollia condensata produces a strikingly shiny blue fruit. The researchers discovered that the Pollia fruit reflects back 30% of the light cast on it. Furthermore, its reflective properties stand the test of time in a remarkable way.