Transmission electron micrograph (TEM) of granal stacks (black membranous threads) in a chloroplast of the coleus leaf, ^IColeus blumei. ^i The chloroplast is the unit within the leaf that manufactures the food supply (starch) of the plant during the process of photosynthesis. The granal stacks contain photosynthetic pigments (chlorophyll), which convert the sun's energy into chemical energy. The grana are connected at points called frets (dark bands), which are embedded in the matrix of the chloroplast. The white area at centre containing fine fibrils, is a nucleoid, the site of DNA synthesis in a chloroplast. Mag: X 200,000 at 10x8 inch size.