Chloroplasts are specialized organelles found in all higher plant cells. These organelles contain the plant cell & chlorophyll responsible for the plant's green color and the ability to absorb energy from sunlight. This energy is used to convert water plus atmospheric carbon dioxide into metabolize sugars by the biochemical process of photosynthesis. Chloroplasts have a double outer membrane. Within the stroma are other membrane structures - the thylakoids. Thylakoids appear in stacks called "grana" (singular = granum).
Chloroplasts capture light energy from the sun to produce the free energy stored in ATP and NADPH through a process called photosynthesis. (ATP is a member of a group of organic compounds containing phosphate groups that are linked by means of “energy rich” chemical bonds.) (Nicotinamide Adenine Dinucleotide Phosphate Hydrogen)