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 green cells, each a separate compartment whose boundary consists of two membranes, the interior of the inner membrane of which contains a liquid 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.