Chloroplasts are one of the many different types of organelles in the cell. They are thought to have originated as endosymbiotic cyanobacteria. This was first suggested by Konstantin Mereschkowski in 1905 after an observation by Schimper in 1883 that chloroplasts closely resembled cyanobacteria. Almost all chloroplasts are thought to derive directly or indirectly from a single endosymbiotic event. 