Leaves display a remarkable range of forms from flat sheets with simple outlines to the cup-shaped traps found in carnivorous plants. A general question in developmental and evolutionary biology is how tissues shape themselves to create the diversity of forms we find in nature such as leaves, flowers, hearts and wings. Study of leaves has led to progress in understanding the mechanisms that produce the simpler, flatter forms. But it’s been unclear what lies behind the more complex curved leaf forms of carnivorous plants. Previous studies using the model species Arabidopsis thaliana which has flat leaves revealed the existence of a polarity field running from the base of the leaf to the tip, a kind of inbuilt cellular compass which orients growth. To test if an equivalent polarity field might guide growth of highly curved tissues, researchers analysed the cup-shaped leaf traps of the aquatic carnivorous plant Utricularia gibba, commonly known as the humped bladderwort. The team of Professor Enrico Coen used a combination of 3D imaging, cell and clonal analysis and computational modelling to understand how carnivorous plant traps are shaped. These approaches showed how Utri...