Chloroplast

Most living cells of so-called higher plants contain a number of tokens of a type of plastid called chloroplasts, tiny, somewhat football-shaped, bacteria-sized organelles, a few micrometers in size, up to several hundred in number in the specialized green cells, each chloroplast a separate compartmented structure whose boundary consists of two membranes, the interior of the inner membrane of which contains a semiliquid matrix, called stroma, suspending a system of membranes, called thylakoids, whose membranes embed molecules of chlorophyll and other pigments that absorb energy from sunlight, initiating the physico-chemical process of photosynthesis.

Other organisms thathouse chloroplasts and perform photosynthesis:

• algae, mostly single-celled, members of the plant kingdom;
• diatoms and euglenids, among the protists, a mixed group of mostly single-celled eukaryotic organisms that do not fall under the eukaryotic kingdoms of plants, fungi and animals.