Variation among vascular plants in the initiation and patterning of leaves results in a diverse array of leaf shape, including the strap-like leaf of many grasses and the broad lamina of most eudicots. Recent findings highlight the importance of interactions between the shoot apical meristem (SAM) and developing leaf primordia in axis specification and the establishment of leaf shape. Global regulators of epigenetic states have been implicated in these interactions and may play a role in distinguishing founder cells and stem cells within the SAM.