Stomata are tiny pores in the epidermis of most land plants that allow regulated gas exchange between the environment and the plant interior, as well as water evaporation. In Arabidopsis, stomatal development requires the sequential function of the three related basic helix-loop-helix transcription factors FAMA, MUTE and SPEECHLESS (SPCH), but how is it controlled in other plants? On p. 2265, Dominique Bergmann and co-workers report that orthologues of all three transcription factors exist in rice and maize, and that the function of FAMA is evolutionarily conserved. The authors first identify ArabidopsisFAMA, MUTE and SPCH homologues in rice and maize through in silico analysis and then analyse their function by studying their expression and through mutation, complementation and overexpression approaches. FAMA function is conserved between Arabidopsis and grasses; in both cases, deleting FAMA prevents stomatal differentiation and morphogenesis. MUTE and SPCH functions, however, differ between grasses and Arabidopsis. Future work should shed further light on the regulation of stomatal development in grasses and other agriculturally important plants.