Virus is a microscopic organism that lives in a cell of another living thing. Although viruses are extremely small and simple, they are a major cause of disease. Some viruses infect human beings with such diseases as measles, influenza, and the common cold.
Passive Mobs. Passive mobs are composed of creatures that will never, under any circumstances, attack the player. Some passive mobs can be bred to create more of them, e.g. pigs can be bred to effectively farm them.
Cultured pearls can be farmed using two very different groups of bivalve mollusk : the freshwater river mussels, and the saltwater pearl oysters. Pearls are considered to be an important part of making ornaments since ancient times.