The chloroplasts are the green plastids present in the plants and certain algae. It is the site of photosynthesis where the plants produce the photosynthate from the carbon dioxide and water. The chloroplast is green in colour due to the presence of chlorophyll. The size and shape of the chloroplast varies. This is surrounded by two membranes which are lipo proteinaceous in nature. The space between the two membranes is known as the periplastidal space. The proteinaceous fluid is filled inside the chloroplast, it is known as the stroma. The stroma contains ribosomes, osmophilic granules, DNA and RNA molecules. Number of membrane bound sac like structures distributed in the stroma, they are known as the lamellae or thylakoids. Thylakoids maybe seen as group, each group is granum. Each member in the granum is known as the grana thylakoid or grana lamellae. The thylakoids are arranged one above the other. The membrane which interconnects the adjacent grana is known as the fret membrane. The chlorophyll is present inside the thylakoid. On the thylakoid small rounded photosynthetic unit or quantosome are present. These are the small photosynthetic units which are capable of bringing out light reaction. Each quantosome possess 200-300 chlorophyll molecules. Quantosome are necessary for photochemical reaction.