The rate, orientation and direction of cell growth and division determine the shape that a given tissue will adopt. In the March 13 Nature Anne-Gaelle Rolland-Lagan and colleagues at the John Innes Centre, Norwich, UK, describe using a clonal analysis to investigate the role of cell growth in the development of asymmetric petals in the plant Antirrhinum (snapdragon) (Nature 2003, 422:161-163). Measurements of the spatiotemporal changes in cell proliferation and anisotropy (the preferential direction of growth) were combined with computational modelling. They found that the direction of growth rather than regional differences in growth rate (cell doubling time) dictated petal asymmetry. In an accompanying review, Claude Desplan and Thomas Lecuit draw striking parallels with analysis of wing formation in Drosophila and comment that the snapdragon study "provide[s] a simple, quantitative, dynamic model in which just a few parameters are sufficient to explain the final shape of the tissue."