Photosynthesis takes place in organelles called chloroplasts. They are about 5µm in length. They are oval structures with double outer membranes. Inside the chloroplast there is a watery matrix called the Stroma. The stroma contains membrane structures called Thylakoids which are disc shaped. These thylakoids, stacked together form a granum. The grana are linked or seperated by membranes called lamellae. The grana absorb the light energy needed for photosynthesis. The glucose made during photosynthesis is stored as starch and so there are usually several starch granules inside the stroma. There is only one granum per layer so as to maximise the surface area.