Coloured transmisson electron micrograph of a chloroplast (green) sitting in the cytoplasm of a pea plant Pisum sativum. The chloroplast is the site of photosynthesis where carbohydrates are obtained from carbon dioxide using the energy from sunlight. The chloroplast is bound by a double membrane. Internally, it consists of stacks of flattened membranes called grana (threadlike) suspended in a matrix of hydrophilic proteins. The grana contain the chlorophyll pigments and are the sites of light reactions during photosynthesis. The orange at left is part of a nucleus and the orange strip at right is the cell wall. Magnification: x1680 at 6x4.5cm size.