3-D animation of a four-celled grass stomatal complex imaged by confocal microscopy. Two central, dumbbell-shaped "guard cells" are flanked by one extra cell on each side, the 'subsidiary cells'. The stomatal complex is surrounded by elongated epidermal cells. Stomata act like cellular leaf valves that balance carbon dioxide uptake and water vapor loss and the four-celled, grass-specific form allows grasses to do this very efficiently. The 3-D reconstruction is depth color coded.