When sea monkeys first hatch, they are approximately the size of a period at the end of a sentence, but they can grow to reach up to 2 inches in length as adults. Sea monkeys can either mate to become pregnant or fertilize their own eggs through parthenogenesis.
Sea monkeys aren't actually monkeys at all, but a genetically altered species of brine shrimp, or Artemia salina. Their creator, Harold von Braunhut, noticed brine shrimp, which was sold as food in a pet store, in the 50s. Fascinated by the way that the species go into suspended animation until they are revived by water, he came up with the idea to market the dried shrimp as pets.
Sea monkeys do not occur in nature, but result instead from crossbreeding to develop a species that is hardier and more suitable for growing in a home tank or fish bowl. Sea monkeys come with a special nutrient powder that must first be used to treat the water for 24 hours before adding the dried eggs. Because the sea monkeys are so small when they hatch, the eggs are treated with a special dye that allows the sea monkeys' owner to see them in the tank.