All grasses exhibit a characteristic strap shaped leaf blade but this consistent external morphology masks an underlying anatomical difference that distinguishes species that carry out C4 versus C3 photosynthesis. A multi-national effort aimed at introducing components of C4 photosynthesis into the C3 plant rice requires an understanding of the genetic regulation of C4 leaf development, so that leaf anatomy can be manipulated in rice. I will provide an overview of our current understanding of C4 leaf development, discuss recent research aimed at identifying genetic regulators of leaf anatomy, and illustrate how this research fits into the wider ‘C4 Rice Project’.