Transmission electron micrograph of a chloroplast in a bean leaf. Chloroplasts are small compartments (organelles) which contain chlorophyll and are found in some plant and algae cells. They are the site of photosynthesis, the process by which plants produce energy from light. The chloroplast (large oval structure; right hand side of image; green), grana (darker, thicker stacks of membranes which look like stacks of parallel lines inside the chloroplast) and lamellae (individual membranes seen in the grana) are visible here. Width of image is 4.5 micrometres.