Yeast microbes are probably one of the earliest domesticated organisms. Microorganisms also make up the microbiota found in and on all multicellular organisms. Microorganisms can form an endosymbiotic relationship with other, larger organisms. Marine cyanobacteria include the smallest known photosynthetic organisms. A few species are parasitic on other marine organisms. Plant cells are quite different from the cells of the other eukaryotic organisms. Introns are found in the genes of most organisms and many viruses. Plants have some of the largest genomes among all organisms. The Neoproterozoic was a time of remarkable diversification of multicellular organisms, including animals. It was the start of development of communal living among organisms, the multicellular organisms. Variation exists within all populations of organisms. Viruses play an important role as vectors for inserting genetic information into other organisms. Aquaculture now provides approximately half of all harvested aquatic organisms. Propylene glycol exhibits a low degree of toxicity toward aquatic organisms. Enzymes serve a wide variety of functions inside living organisms.