A large enclosure of aggregated pigment, typically bacteriochlorophyll c (BChl c), that acts as a light-harvesting antenna structure and is characteristic of green photosynthetic bacteria (e.g. Chlorobiaceae). The BChl aggregates are organized into lamellar elements by pigment-pigment rather than pigment-protein interactions. Chlorosomes also contain BChl a, carotenoids, quinones, lipids, and proteins, and are attached to the cytoplasmic membrane via a BChl a-containing protein baseplate.