Mitochondria and Plastids are membrane-bound organelles that convert energy from foodstuffs (mitochondria and non-photosynthetic plastids) or sunlight (chloroplasts) into cellular energy. Some plastids may also be used for starch storage and the synthesis of fatty acids and terpenes. Organelles likely evolved from bacteria that were endocytosed by nucleated ancestral cells. Metazoan, plant, fungal and other mitochondrial and plastid genomes tend to vary greatly in size and gene content with some of the genes required for the energy creating processes being made by the nuclear genome and imported. Many organisms use one genetic code to translate nuclear mRNAs, and a second one for their mitochondrial and plastid mRNAs. Organelles have their own independent genome that encodes a range of genes directly related to producing energy for the cell.