This microphotograph shows a cross-section of a blade of grass, and the structures inside. Some of those structures are vascular bundles, and they're showing their little smiley faces! Maybe they are happy because they have water. In a discussion at StackExchange, those who know say this is one of the species of grass that has adapted to live in dry areas, such as a desert, and the blade curls up to protect the side that absorbs water. A commenter named Always Confused tells us more about the grass.
The 2 sides of the leaf develop into different structure. The adaxial ("upper") surface, which in its underneath contain the the soft, green tissue, and the abaxial ("bottom") surface which contains more sclerotic tissue.
Normally, when dry-period runs, the leaf remains rolled in an way, so that soft side stay inwards , concave manner, closed, protected from evaporation. The outer, convex abaxial-face acts as a shield.
When rains come; the leaf work in a manner of bimetallic-strip. The inner (adaxial) surface absorbs water and expands (the "hinge cells" help it); and the inner-face become open. Then the inner-face work as a water-absorption tissue.
When dry-period come-again, the leaves enter their original state.
Another post identifies the species as Ammophila arenaria, or marram grass, used to stabilize sand dunes on the coasts. The color is not true. The specimen was stained to make the structures show up better, which happily highlights the pareidolia. -via reddit