Abstract Chloroplasts are the organelles specialized in carrying out the photosynthetic process, which uses light energy to synthesize organic compounds; for this reason, they are common to all photoautotrophic eukaryotes. Besides the biosynthetic pathways directly related to photosynthesis, such as synthesis of pigments (chlorophylls and carotenoids), conversion of CO2 to carbohydrates and reduction and organization of sulfur and nitrogen, several other metabolic pathways occur in chloroplasts. These organelles produce or participate in the production of a series of essential compounds required by other cell compartments. For instance, they are the primary site of biosynthesis of fatty acids, isoprenoids, tetrapyrroles, and aminoacids, as well as of purines, pirimidines, and pentoses necessary for nucleic acid buildup. Thus, chloroplasts, in addition to photosynthesis, play other essential roles in sustaining the metabolism of the cell and the whole plant. The complexity and variety of chloroplast activities can arise from the fact that this, which is now a cell organelle, was originally an organism.