With bright reds and yellows – and even the occasional white – poppies are very bright and colourful. Their petals, however, are also very thin; they are made up of just three layers of cells. University of Groningen scientists Casper van der Kooi and Doekele Stavenga used microscopy and mathematical models describing how light interacts with petals to find out how the vibrant colours are created. The results will be included in a special edition of the Journal of Comparative Physiology A, which focuses on the relationship between insects and flowers.