Chromatophores are internal membrane systems present in photosynthetic prokaryotes. These develop as membrane lined sacs or thylakoids from plasma membrane. Thylakoid membranes contain photosynthetic pigments in cyanobacteria and purple bacteria. Small sacs or granules containing pigments phycobilin are attached to these membranes. In green bacteria chromatophores are covered by non-unit, non-lipid protein membrane. They are sometimes called chlorosomes.