False-colour transmission electron micrograph of a green chloroplast from a variegated leaf of the plant Coleus blumei. Chloroplasts are the sites of photosynthesis in plants & green algae. Chlorophyll pigments, stimulated by light, initiate a chemical reaction, which leads to the formation of sugar from carbon dioxide. Chloroplasts are usually lens-shaped & bound by two membranes; the inner one is folded into a series of stacks called grana (green, threadlike). Chlorophyll pigments are stored on the grana. The large pink region in the chloroplast is a starch grain, a product of photosynthesis. Magnification: x5000 at 6x4.5cm size.